Open Access

Probing the Structural, Electronic, and Magnetic Properties of Ag n V (n = 1–12) Clusters

Nanoscale Research Letters201712:625

https://doi.org/10.1186/s11671-017-2394-0

Received: 19 October 2017

Accepted: 30 November 2017

Published: 16 December 2017

Abstract

The structural, electronic, and magnetic properties of Ag n V (n = 1–12) clusters have been studied using density functional theory and CALYPSO structure searching method. Geometry optimizations manifest that a vanadium atom in low-energy AgnV clusters favors the most highly coordinated location. The substitution of one V atom for an Ag atom in Ag n + 1 (n ≥ 5) cluster modifies the lowest energy structure of the host cluster. The infrared spectra, Raman spectra, and photoelectron spectra of Ag n V (n = 1–12) clusters are simulated and can be used to determine the most stable structure in the future. The relative stability, dissociation channel, and chemical activity of the ground states are analyzed through atomic averaged binding energy, dissociation energy, and energy gap. It is found that V atom can improve the stability of the host cluster, Ag2 excepted. The most possible dissociation channels are Ag n V = Ag + Ag n − 1V for n = 1 and 4–12 and Ag n V = Ag2 + Ag n − 2V for n = 2 and 3. The energy gap of Ag n V cluster with odd n is much smaller than that of Ag n + 1 cluster. Analyses of magnetic property indicate that the total magnetic moment of Ag n V cluster mostly comes from V atom and varies from 1 to 5 μ B. The charge transfer between V and Ag atoms should be responsible for the change of magnetic moment.

Keywords

Ag n V clusterGrowth behaviorSpectrumElectronic and magnetic property

Background

In the past decades, silver clusters have drawn special attention because of their unusually optical and catalytic properties [120]. Simultaneously, theoretical and experimental investigations have revealed that an atom doped into a small cluster of another element can fundamentally change the nature of the host cluster [2144]. Silver clusters doped with different atoms have been expected to tailor the desired optical, electronic, and magnetic properties for potential applications in imaging, sensing, biology, medicine, and nanotechnology [4555]. For instance, Si doping into silver cluster leads to a broadening and damping of the peaks of UV-visible absorption spectra of Ag clusters [45]. The optical character of Ag n Au m can be adjusted by changing the ratio of silver atoms to gold atoms and Au4Ag4 might be a potentially promising molecular photoelectric device [46]. In contrast with silver clusters, the binary Ag-Au cluster-modified TiO2 electrode improves short-circuit current density and maximum power conversion efficiencies of solar cell [47]. The adsorption energies of a set of typical ligands (−COOH, −CN, −OH, −SH, −CH3, −NO2, −NH3, −NO) are smaller on Ag12Au cluster than on Ag13 cluster [48]. Ag-Cu nanoalloy is a potential candidate to substitute noble Pt-based catalyst in alkaline fuel cells [49]. The electrons in outer atoms of Ag12Cu cluster have a more active characteristic than that of Ag13 cluster [50]. The catalytic activity of Ag-Pd alloy cluster for hydrogen dissociation is closely associated with the stoichiometry. The Ag6Pd2 is the most efficient cluster for hydrogen molecule adsorption and can serve as a promising candidate for H2 storage [51]. The introduction of a single 3d transition-metal atom effectively solved the instability problem of the Ag12 icosahedron [52]. Recently, several investigations have been carried out for V-doped silver clusters on account of their unique physical and chemical properties [5659]. Zhang et al. reported that the neutral Ag12V cluster show larger relative binding energies compared with pure icosahedral Ag13 cluster [56]. Chen et al. found that Pyridine on V@Ag12 clusters exhibits the strongest chemical enhancement with a factor of about a thousand [57]. Medel et al. explored the nature of valence transition and spin moment in Ag n V+ clusters that have an enhanced stability for n = 14 [58]. However, there are relatively few works concerning the neutral V-doped silver clusters. In particular, the various spectra of Ag n V clusters have not been obtained but would be extremely helpful for the identification of cluster structure. The structural motif of V-doped silver clusters is also needed to be further explored. The change of magnetic moment of magnetic impurity embedded in a nonmagnetic host still is not fully understood. Accordingly, in the present paper, the geometrical, electronic, and magnetic properties of Ag n V (n = 1–12) clusters will be systematically researched through density functional theory (DFT). It is hoped that this work can provide a reference for understanding the relationship between the function and structure of materials and for related experiments.

Methods

The accuracy of distinct exchange-correlation functionals, as implemented in GAUSSIAN09 program package (Frisch, M. J. et al., Wallingford, KY, USA) [60], was first verified by calculations on Ag2 dimer. The calculated results based on PW91PW91/LanL2DZ (Perdew, J. P. et al., New Orleans, Louisiana, USA) level are in good agreement with experimental findings [61, 62], as summarized in Table 1. On the other hand, test calculations using the different DFT functionals were performed for AgV dimer. Five functionals listed in Table 1 favor the same spin configurations. Thus, this level of theory is used for geometry optimizations and frequency analyses of Ag n V clusters. A great many initial configurations of Ag n V clusters were constructed by using CALYPSO which is an efficient structure prediction method [63]. In this method, structural evolution is achieved by particle swarm optimization (PSO) that is a population-based stochastic optimization technique. The bond characterization matrix technique is utilized to enhance searching efficiency and remove similar structures. The significant feature of CALYPSO requires only chemical compositions for a given cluster to predict its structure. Due to the spin polarization effect, each initial structure was optimized at possible spin states. If an imaginary vibrational frequency is found, a relaxation of the unstable structure will be done until the local minimum is really obtained. In all computations, the convergence thresholds were set to 6.0 × 10−5 Å for the displacement, 1.5 × 10−5 Hartree/Bohr for the forces and 10−6 Hartree for a total energy.
Table 1

The bond length and electronic properties of Ag2 and V2 dimers

Dimer

Functional/basis set

R(Å)

De(eV)

VIP(eV)

EA(eV)

f(cm−1)

Calc.

Expt.

Calc.

Expt.

Calc.

Expt.

Calc.

Expt.

Calc.

Expt.

Ag2

PW91PW91/LanL2DZ

2.58

2.53a

1.78

1.65a

7.96

7.65a

0.97

1.02a

187.0

192.4a

PBEPBE/LanL2DZ

2.59

 

1.76

 

7.89

 

0.92

 

184.2

 

BP86/LanL2DZ

2.58

 

1.75

 

8.05

 

1.08

 

188.4

 

LSDA/LanL2DZ

2.50

 

2.35

 

8.87

 

1.52

 

215.2

 

B3LYP/LanL2DZ

2.61

 

1.55

 

7.80

 

0.93

 

177.0

 

V2

PW91PW91/LanL2DZ

1.78

1.77b

2.75

2.47 ± 0.22b

6.46

6.35b

0.46

 

657.3

 

aRef. [67]

bRef. [68]

Results and Discussions

Geometrical Structures and Vibrational Spectra

For Ag n V (n = 1–12) clusters, an extensive structural search has been performed and many isomers have been obtained. The most stable structure and two low-lying isomers for each Ag n V cluster are displayed in Fig. 1. According to the energies from low to high, these isomers are denoted by na, nb, and nc, where n represents the number of Ag atoms in Ag n V cluster. Their symmetry, spin multiplicity, and energy difference compared to each of the most stable structures are also indicated in the figure. Some physical parameters of the ground state Ag n V clusters are gathered in Table 2. Meanwhile, in order to examine the effects of dopant V on silver clusters, geometry optimizations of Ag n (n = 2–13) clusters have been accomplished using the same method and basis set. The lowest energy structures of Ag n clusters plotted in Fig. 1 agree well with earlier report [39].
Fig. 1

The ground state structures of Ag n + 1 and Ag n V (n = 2–12) clusters. Two low-lying isomers for Ag n V clusters. The symmetry, spin multiplicity, and energy difference are given below them. The gray and black balls denote Ag and V atoms, respectively

Table 2

The dipole moment (μ), polarizability \( \left({a}_{xx},\kern0.5em {a}_{yy},\kern0.5em {a}_{\mathrm{zz}},\kern0.5em \overline{a}\right) \), zero-point energy (ZPE) and maximum and minimum bond lengths (Rmax, Rmin) of the most stable Ag n V (n = 1–12) clusters and coordination number and average coordination bond length (Rv) for V atom

Clusters

μ (D)

a xx (a.u.)

a yy (a.u.)

a zz (a.u.)

\( \overline{a} \)(a.u.)

ZPE(eV)

N

Rmax (Å)

Rmin (Å)

Rv(Å)

AgV

2.07

100.40

100.40

155.87

118.89

0.01

1

2.61

2.61

2.61

Ag2V

0.89

124.35

182.31

196.44

167.70

0.03

2

2.73

2.72

2.73

Ag3V

1.42

135.44

277.87

178.70

197.34

0.04

3

2.77

2.71

2.76

Ag4V

0.82

132.08

340.88

230.06

234.34

0.06

4

2.79

2.70

2.73

Ag5V

0.62

327.29

292.90

165.77

261.99

0.08

5

2.82

2.70

2.74

Ag6V

0.74

332.60

325.89

245.02

301.17

0.10

6

2.91

2.72

2.77

Ag7V

0.21

391.20

340.25

258.36

329.94

0.12

7

3.02

2.73

2.80

Ag8V

0.35

417.09

378.36

276.02

357.16

0.14

8

2.88

2.77

2.79

Ag9V

0.41

423.10

423.10

300.90

382.37

0.16

9

2.94

2.75

2.80

Ag10V

0.77

424.83

364.25

451.18

413.42

0.18

10

3.01

2.76

2.79

Ag11V

0.59

402.07

440.99

442.18

428.41

0.20

11

3.13

2.75

2.77

Ag12V

0

440.39

439.34

441.45

440.39

0.22

12

3.04

2.76

2.77

The optimized results for AgV dimer show that the quintet spin state is energetically lower than the triplet and septet spin states by 0.92 and 1.47 eV, respectively. Therefore, the quintet AgV is the ground state structure. The most stable structure of Ag2V cluster is the triangular 2a with C2v symmetry. The 2a configuration in quartet spin state becomes the 2b isomer. The 3a and 4a isomers, which resemble the lowest energy structures of Ag4 and Ag5 clusters, are the ground state of Ag3V and Ag4V clusters. The ground state structure of Ag4V cluster is also in accord with the result of Medel et al. [58]. The 4b isomer with V atom on the top is a square pyramid and the first three-dimensional (3D) structure. The 4c isomer possesses a triangular bipyramid structure, and its total energy is above the 4a isomer by 0.49 eV. Other planar and 3D isomers are less stable than 4c isomer.

Starting from n = 5, the lowest energy structures of Ag n V clusters prefer 3D configurations. To prevent from leaving out the ground state, we had also utilized the optimized strategies of substituting an Ag by one V atom from the stable silver cluster or adding Ag atom(s) to small Ag n V clusters. The 5a and 6a isomers are the most stable structures of Ag5V and Ag6V clusters. The two isomers are obtained by distorting the geometry from C5v and C2v to Cs and C2 point groups, respectively. The 6a isomer is 0.62 eV lower in quartet spin state than in sextet spin state. The 5c and 6b isomers are similar to the ground state structures of pure Ag6 and Ag7 clusters. The 6b isomer is almost degenerate with the 6a isomer. Owing to the Jahn–Teller effect, the planar 6c isomer with C2h symmetry has a slight deviation from D2h symmetry.

With regard to Ag n V (n = 7–12) clusters, the number of isomers increases rapidly with the increase of cluster size. The optimized structures indicate that the energies of Ag n V clusters with the same configuration increase with the decrease of the coordination number of V atom. As a result, various Ag n V isomers where V atom occupies the position with the highest coordination number were considered further to make sure that the most stable structures are the global minimum. The lowest energy structures of Ag7V, Ag8V, Ag9V, Ag10V, Ag11V, and Ag12V clusters are 7a, 8a, 9a, 10a, 11a, and 12a in Fig. 1, respectively. Their geometries are qualitatively in accord with results of Medel et al. [58]. These structures are entirely different from the ground state structure of the corresponding Ag n + 1 clusters and contain a pentagonal bipyramid. The Ag n V isomers which correspond to the lowest energy structures of Ag n + 1 clusters lay above each of the ground state structures (na). In addition, the 10b and 12a have a slight deviation from D5d and D3d symmetry. The cage configuration of Ag12V cluster, where V atom occupies the central position, is discovered only in the lowest spin states.

From the optimized results, it is found that the Ag n V clusters have an obvious growth law. The trapezoid and icosahedron are two basic frameworks for the growth process of Ag n V cluster, as shown in Fig. 2. The two- to three-dimensional structural transition for Ag n V cluster occurs at n = 5. The transition size of Ag n V cluster is smaller than that of pure Ag clusters (n = 6). For n = 5–12, the ground states of Ag n V clusters are obviously distinct from those of the Ag n + 1 clusters. The V atom in Ag n V cluster tends to occupy the most highly coordinated position and is gradually encapsulated in the center by the Ag atoms. This may be attributed to the principle of maximum overlap in chemical bond theory of complexes. Because Ag and V atoms have more orbital overlap under the above circumstances, the energy of Ag n V cluster, which is also related to the arrangement of Ag atoms, will be lower and then the corresponding cluster is more stable.
Fig. 2

The growth diagram of Ag n V (n = 1–12) clusters

The infrared and Raman spectroscopy are powerful tools for the identification of cluster structure and material component. Generally, the structural identification is accomplished by comparing experimental findings with theoretical predictions which is an indispensable part. Accordingly, the infrared spectra and Raman spectra of the most stable Ag n V (n = 1–12) clusters are displayed in Fig. 3. The infrared spectrum shows asymmetric vibrations of polar group. Raman spectrum reveals the symmetric vibrations of nonpolar group and skeleton. The AgV dimer have the same infrared and Raman spectra. For other Ag n V clusters, the strong absorption location of infrared spectrum has a weak peak in Raman scattering spectrum. On the contrary, the Raman scattering peak is strong and the infrared absorption is weak. The peak position in the two kinds of spectra for all isomers are in the range of 15~270 cm−1. The most intense peak in the infrared spectrum of each Ag n V clusters is related to the Ag-V stretching vibration.
Fig. 3

The infrared spectra (black) and Raman spectra (red) of the ground state and two low-lying isomers of Ag n V (n = 1–12) clusters

Electronic Properties

The vertical ionization potential (VIP) and electron affinity (EA) are two primary quantities to probe the electronic properties and can be calculated as follows:
$$ \mathrm{VIP}=E\left(\mathrm{cationic}\ \mathrm{cluster}\right)-E\left(\mathrm{cluster}\right) $$
(1)
$$ \mathrm{EA}=E\left(\mathrm{cluster}\right)-E\left(\mathrm{anionic}\ \mathrm{cluster}\right) $$
(2)
where E(cationic cluster) and E(anionic cluster) are the single-point energies of cationic and anionic clusters in the geometry of neutral cluster. For the lowest energy Ag n + 1 and Ag n V clusters, Table 3 lists the calculated VIP, EA, and the available experimental values. The calculated VIPs and EAs of Ag n + 1 clusters are in line with their measured data. This consistency confirms the reliability of the current theoretical approach again. Moreover, we note that AgV dimer has the biggest VIP and the smallest EA. This implies that AgV is hard to lose or require an electron. The icosahedral Ag12V cluster has the biggest EA and is easy to get one more electron. To offer reference material for photoelectron spectroscopy experiment in the aftertime, the theoretical photoelectron spectra (PES) of the ground state and two low-lying structures of Ag n V (n = 1–12) clusters were simulated by adding the first VIP to each occupied orbital energy relative to the HOMO and fitting them with a Lorentz expansion scheme and a broadening factor of 0.1 eV, as shown in Fig. 4. The distribution of energy level of these clusters is in the range of 5.5 to 12 eV. The experimenters can make use of the PES spectra to distinguish these clusters.
Table 3

VIP and VEA of the ground state Ag n + 1 and Ag n V clusters. The data in parentheses are experimental findings

Clusters

VIP(eV)

VEA(eV)

Clusters

VIP(eV)

VEA(eV)

Ag2

7.96

0.97

AgV

7.04

0.82

Ag3

6.92(6.20a)

2.17

Ag2V

5.99

1.28

Ag4

6.60(6.65a)

1.63

Ag3V

6.35

1.49

Ag5

6.28(6.35a)

2.04

Ag4V

6.33

1.86

Ag6

7.15(7.15a)

1.33

Ag5V

6.09

1.47

Ag7

6.06(6.40a)

1.94

Ag6V

6.32

1.87

Ag8

6.99

1.17

Ag7V

5.89

1.69

Ag9

6.01

2.27

Ag8V

5.79

1.87

Ag10

5.95

1.66

Ag9V

5.87

2.08

Ag11

5.86

2.42

Ag10V

5.88

2.24

Ag12

6.13

2.09

Ag11V

5.83

2.31

Ag13

5.61

2.36

Ag12V

5.99

2.45

aRef. [67]

Fig. 4

Simulated PES of the ground state and two low-lying isomers of Ag n V (n = 1–12) clusters

In order to examine the influence of V atom on the stability of silver clusters, the atomic averaged binding energies (E b) of the most stable Ag n + 1 and Ag n V clusters can be estimated as follows:
$$ {E}_b\left({\mathrm{Ag}}_{n+1}\right)=\left[\left(n+1\right)E\left(\mathrm{Ag}\right)-E\left({\mathrm{Ag}}_{n+1}\right)\right]/\left(n+1\right), $$
(3)
$$ {E}_{\mathrm{b}}\left({\mathrm{Ag}}_n\mathrm{V}\right)=\left[ nE\left(\mathrm{Ag}\right)+E\left(\mathrm{V}\right)-E\left({\mathrm{Ag}}_n\mathrm{V}\right)\right]/\left(n+1\right), $$
(4)
where E(Ag), E(Ag n + 1), E(V), and E(Ag n V) are the energies of Ag atom, silver cluster, V atom, and AgnV cluster, respectively. The calculated binding energies per atom for the most stable Ag n + 1 and Ag n V clusters are plotted in Fig. 5. It is clear from this figure that the E b of Ag n V cluster is a monotonically increasing function of the cluster size and larger than that of Ag n + 1 cluster for n ≥ 2. Especially, the E b of doped cluster increase rapidly for the planar structures and gradually for the 3D structures. This means that the bonding force among atoms becomes stronger and stronger in the process of growth. The substitution of a V atom for an Ag atom in Ag n + 1(n ≥ 2) clusters can evidently enhance the stability of the host clusters. On the other hand, the bond energy of diatomic cluster should be closely related to the bond length. The E b of AgV dimer is smaller than that of Ag2. The abnormal change may be ascribed to the fact that the bond distance of AgV (2.61 Å) is longer than that of Ag2 (2.58 Å).
Fig. 5

The averaged binding energies of the lowest energy Ag n + 1 and Ag n V (n = 1–12) clusters

The thermal stability of clusters can be examined by the dissociation energy (DE), which is different for the distinct dissociation channels. The most basic dissociation channel is the splitting of a larger cluster into two smaller clusters. The corresponding DE is small relative to other dissociation channel. Hence, the subsequent dissociation channels are investigated for the most stable Ag n V (n = 1–12) clusters.
$$ {\mathrm{Ag}}_n\mathrm{V}\to {\mathrm{Ag}}_m+{\mathrm{Ag}}_{n-m}\mathrm{V} $$
(5)
where m is not more than n. The DEs of the above dissociation channels are defined as follows:
$$ {\mathrm{DE}}_m\left({\mathrm{Ag}}_n\mathrm{V}\right)=E\left({\mathrm{Ag}}_m\right)+E\left({\mathrm{Ag}}_{n-m}\mathrm{V}\right)-E\left({\mathrm{Ag}}_n\mathrm{V}\right) $$
(6)
where E represents the energy of the corresponding cluster or atom. The DEs of Ag n V clusters for the different dissociation channels have been listed in Table 4. The small DE indicates that corresponding dissociation channel is easy to take place. That is to say, the dissociation channel corresponding to the minimum DE is most likely to occur. It can be seen from Table 4 that the most preferred dissociation channels of Ag n V clusters are Ag n V = Ag + Ag n − 1V for n = 1 and 4–12 and Ag n V = Ag2 + Ag n − 2V for n = 2 and 3. The minimum DE (2.54 eV) of Ag12V cluster is biggest in all doped cluster, implying that the icosahedral cluster is more stable than other cluster. In addition, we find that the change trend of the minimum DE of the 3D neutral Ag n V (n = 5–12) cluster is the same as that of abundances of the cationic Ag n V+ cluster [64, 65]. However, there is no such relationship between planar Ag n V and Ag n V+ for n = 2–4.
Table 4

The dissociation energy (DE, eV) of Ag n V clusters for the distinct dissociation channels

Ag n V clusters dissociation channel

DE

n = 1

DE

n = 2

DE

n = 3

DE

n = 4

DE

n = 5

DE

n = 6

DE

n = 7

DE

n = 8

DE

n = 9

DE

n = 10

DE

n = 11

DE

n = 12

AgV = Ag n  + Ag1 − n V

1.70

           

Ag2V = Ag n  + Ag2 − n V

1.43

1.36

          

Ag3V = Ag n  + Ag3 − n V

1.98

1.63

2.48

         

Ag4V = Ag n  + Ag4 − n V

1.94

2.13

2.72

2.44

        

Ag5V = Ag n  + Ag5 − n V

2.05

2.21

3.33

2.79

2.82

       

Ag6V = Ag n  + Ag6 − n V

1.99

2.26

3.35

3.35

3.10

2.53

      

Ag7V = Ag n  + Ag7 − n V

2.22

2.43

3.63

3.59

3.89

3.05

3.14

     

Ag8V = Ag n  + Ag8 − n V

2.10

2.54

3.68

3.75

4.02

3.72

3.54

3.14

    

Ag9V = Ag n  + Ag9 − n V

2.15

2.47

3.84

3.86

4.23

3.90

4.26

3.45

3.84

   

Ag10V = Ag n  + Ag10 − n V

2.03

2.40

3.65

3.90

4.21

3.99

4.31

4.05

4.17

3.75

  

Ag11V = Ag n  + Ag11 − n V

2.35

2.60

3.90

4.02

4.57

4.29

4.72

4.42

5.09

4.39

4.41

 

Ag12V = Ag n  + Ag12 − n V

2.54

3.11

4.29

4.46

4.89

4.84

5.21

5.02

5.65

5.50

5.24

4.80

The energy gap (E g) between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is always considered to be an important quantity that characterizes the chemical activity of the small metal clusters. A large energy gap is related to a high chemical stability. For the ground state Ag n + 1 and Ag n V clusters, Fig. 6 shows the energy gaps as a function of the cluster size. An odd-even alternation is observed in the energy gaps of pure silver clusters. This alternation can be explained by the electron pairing effect, i.e., the electron shielding effect of two electrons occupying the same HOMO is much smaller than that of two electrons occupying different orbits. An Ag atom ([Kr]4f144d 105s 1) in Ag n + 1 cluster is substituted by a V ([Ar]3d 34s 2) atom. For odd n, the closed shell of Ag n + 1 cluster is replaced by the open shell of Ag n V cluster. Of course, the E g of Ag n V cluster with odd n is less than that of Ag n + 1 cluster. This decrease is very obvious. For even n, both Ag n + 1 and Ag n V clusters have an unrestricted shell. The E g should depend on their structures. In this case, we note that the E g of Ag n V (n = 2 and 4) cluster with planar structure is smaller than that of Ag n + 1 cluster and the E g of Ag n V (n = 6, 8, 10, and 12) cluster with 3D structure is a little bigger than that of Ag n + 1 cluster. In general, the substitution of one V atom for an Ag atom in Ag n + 1 clusters with even n has little effect on the energy gap of the host cluster.
Fig. 6

The HOMO-LUMO energy gaps of the ground state Ag n + 1 and Ag n V (n=1–12) clusters

Magnetic Properties

The magnetic property of cluster is frequently used in the preparation of nanoelectronic devices and high-density magnetic storage materials. The total magnetic moment of cluster consists of the spin magnetic moment and orbital magnetic moment of electrons. The spin magnetic moment of an electron is much greater than the orbital magnetic moment, and thereby, the magnetic moment of cluster is dominated by the spin magnetic moment. The total magnetic moment of the lowest energy Ag n V clusters (n = 1–12) clusters has been calculated and are presented in Fig. 7, where we have also plotted the total magnetic moment of the host clusters. The magnetic moments of the most stable Ag n + 1 clusters are completely quenched for odd n and are 1 μB for even n. The small Ag n V clusters have a large magnetic moment. With the increase of the cluster size, the magnetic moment of Ag n V clusters decreases in waves. When n = 12, the Ag12V has the same magnetic moment as Ag13 cluster. This means that the doping of V atom can only enhance the magnetism of small silver clusters. As an effort to account for the magnetism, Fig. 8 shows the spin density of states (SDOS) for the ground state Ag n V clusters. It is obvious from this figure that the Ag n V clusters have some magnetic domains which decrease with the increase of clusters size. All the lowest energy structures have a strong band between − 5 eV and − 2.5 eV, which is composed mainly of the valence s and d orbitals of the Ag and V atoms. The energy levels near the HOMO, E − E HOMO =  − 1~0 eV, act as a key role in the determination of magnetic behavior of Ag n V clusters.
Fig. 7

Total magnetic moment of the ground state Ag n + 1 and Ag n V (n = 1–12) clusters and local magnetic moment on V atom

Fig. 8

The SDOS of ground state Ag n V (n = 1–12) clusters. Spin up is positive and spin down is negative. A broadening factor δ = 0.1 eV is used. Spin up minus spin down is the blue part. The dashed line indicates the location of the HOMO level

To explore the magnetic properties further, we have carried out the natural bond orbital analysis for the most stable Ag n V clusters [66]. The local magnetic moments on V atom are 4.18 μ B for AgV, 4.41 μ B for Ag2V, 4.03 μ B for Ag3V, 3.36 μ B for Ag4V, 3.78μ B for Ag5V, 3.40 μ B for Ag6V, 3.73 μ B for Ag7V, 3.33 μ B for Ag8V, 2.91 μ B for Ag9V, 3.29 μ B for Ag10V, 2.77 μ B for Ag11V, and 2.08 μ B for Ag12V, as shown in Fig. 7. Overall, the magnetic moment of V atom gradually decreases with the size of clusters increasing. The magnetic moment provided by Ag atoms is very small. Furthermore, except for Ag2V, Ag5V, and Ag7V clusters, the total magnetic moment of Ag atoms in other doped clusters exhibit the antiferromagnetic alignment with respect to the V atom’s magnetic moment. In other words, the total magnetic moments of all Ag n V clusters are chiefly derived from the paramagnetic V atom, as shown in Fig. 7.

The local magnetic moment and charge on 4s, 3d, 4p, and 4d shells of V atom in the lowest energy Ag n V cluster are listed in Table 5. One can be seen from this table that the partially occupied 3d shell play a crucial role in determining the magnetism of V atom and its magnetic moment is 2.01~3.82 μ B. The 4s and 4p shells, which are nonmagnetic for a free V atom, produce a little of the magnetic moment. The 4d shell is almost non-magnetic. The charge on 3d and 4p shells increases by 0.77–1.97 and 0.03–2.41 e respectively. Especially, the charge on the 4p orbital increases with the increase of the clusters size. A very few charge is found on the 4d orbit of V atom in Ag n V (n = 4–12) cluster. Nevertheless, the charge on 4s shell reduces by 1.02–1.54 e. The charge transfer hints that V atom in Ag n V clusters has a hybridization among s, p, and d shells. As we know, the isolated V atom has five valence electrons. At the same time, the charge of V atom in Ag n V cluster can be obtained from Table 5. From the principle of charge conservation, 0.10–0.21 e transfer from V atom to Ag atoms for the planar Ag n V (n = 1–4) clusters, whereas 0.35–2.92 e from Ag atoms to V atom for the 3D Ag n V (n = 5–12) clusters, as shown in Fig. 9. If M and C denote the magnetic moment and valence electron of V atom in Ag n V clusters, both the variation of magnetic moment (ΔM = M − 3) and charge transfer (ΔC = 5 − C) have the same changing trend, as displayed in Fig. 10. It can be concluded from Fig. 10 that charge transfer should be the reason for the modification of the magnetic moment of V atom in Ag n V clusters.
Table 5

The charge (Q) and local magnetic moment (M) of 4s, 3d, 4p, and 5d states for the V atom in the ground state Ag n V clusters

Clusters

s–V

3d–V

4p–V

4d–V

Q(e)

M (μB)

Q(e)

M (μB)

Q(e)

M (μB)

Q(e)

M (μB)

AgV

0.98

0.48

3.79

3.69

0.03

0.01

0

0

Ag2V

0.81

0.53

3.92

3.82

0.12

0.06

0

0

Ag3V

0.64

0.32

3.90

3.68

0.25

0.03

0

0

Ag4V

0.58

0.04

3.77

3.31

0.53

0.01

0.02

0

Ag5V

0.49

0.07

4.03

3.65

0.82

0.06

0.01

0.01

Ag6V

0.46

0.04

4.00

3.34

0.92

0.02

0.02

0

Ag7V

0.47

0.07

4.14

3.56

1.12

0.10

0.02

0

Ag8V

0.48

0.04

4.22

3.20

1.33

0.09

0.02

0

Ag9V

0.47

0.03

4.34

2.80

1.53

0.07

0.03

0.01

Ag10V

0.50

0.06

4.53

3.11

1.94

0.12

0.04

0

Ag11V

0.50

0.04

4.74

2.64

2.25

0.09

0.04

0

Ag12V

0.50

0.02

4.97

2.01

2.41

0.05

0.04

0

Fig. 9

The charge transfer of V atom in the most stable Ag n V (n = 1–12) clusters. Free V atom as the reference point

Fig. 10

The charge transfer (ΔC) and the change of magnetic moment (ΔM) of V atom in the most stable Ag n V (n = 1–12) clusters

Conclusions

The structural, electronic, and magnetic properties of Ag n V (n = 1–12) clusters have been investigated on the basis of DFT and CALYPSO structure searching method. The results indicate V atom in the lowest energy Ag n V cluster tends to occupy the position with the highest coordination number. The substitution of an Ag atom in Ag n + 1 (n ≥ 5) cluster by one V atom changes the geometry of the host clusters. The infrared spectra, Raman spectra, and PES of Ag n V (n = 1–12) clusters are expected to identify the ground states in times to come. Aside from AgV, the stability of other Ag n V cluster is higher than that of Ag n + 1 cluster. The relatively easy dissociation channels are Ag n V = Ag + Agn − 1V for n = 1 and 4–12 and Ag n V = Ag2 + Ag n − 2V for n = 2 and 3. The chemical activity of Ag n V cluster with odd n is higher than that of Ag n + 1 clusters. The magnetic moments of Ag n V clusters originate mainly from the doped V atom and decrease gradually from 5 to 1 μ B with the increase of cluster size. The change of magnetic moment may be attributed to the charge transfer between V and Ag atoms.

Abbreviations

3D: 

Three-dimensional

DE: 

Dissociation energy

DFT: 

Density functional theory

EA: 

Electron affinity

HOMO: 

Highest occupied molecular orbital

LUMO: 

Lowest unoccupied molecular orbital

PSO: 

Particle swarm optimization

VIP: 

Vertical ionization potential

Declarations

Funding

This project was supported by the National Natural Science Foundation of China (11574220) and by Innovation Project in Sichuan Province.

Authors’ Contributions

DD, RX, and Y-GX conceived the idea. RX, LX, and X-YS performed the calculations. DD and RX wrote the manuscript and all authors contributed to revisions. All authors read and approved the final manuscript.

Competing Interests

The authors declare that they have no competing interests.

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Authors’ Affiliations

(1)
School of Science, Xihua University, Chengdu, China

References

  1. Molina B, Tlahuice-Flores A (2016) Thiolated Au18 cluster: preferred Ag sites for doping, structures, and optical and chiroptical properties. Phys Chem Chem Phys 18:1397–1403View ArticleGoogle Scholar
  2. Gomez LF, O’Connell SMO, Jones CF, Kwok J, Vilesov AF (2016) Laser-induced reconstruction of Ag clusters in helium droplets. J Chem Phys 145:114304View ArticleGoogle Scholar
  3. Lethiec CM, Madison LR, Schatz GC (2016) Dependence of plasmon energies on the acoustic normal modes of Agn (n=20, 84, and 120) clusters. J Phys Chem C 120:20572–20578View ArticleGoogle Scholar
  4. Chen J, Zhang HY, Liu XH, Yuan CQ, Jia MY, Luo ZX, Yao JN (2016) Charge-transfer interactions between TCNQ and silver clusters Ag20 and Ag13. Phys Chem Chem Phys 18:7190–7196View ArticleGoogle Scholar
  5. Urushizaki M, Kitazawa H, Takano S, Takahata R, Yamazoe S, Tsukuda T (2015) Synthesis and catalytic application of ag44 clusters supported on mesoporous carbon. J Phys Chem C 119:27483–27488View ArticleGoogle Scholar
  6. Buceta D, Busto N, Barone G, Leal JM, Dominguez F, Giovanetti LJ, Requejo FG, Garcia B, Lopez-Quintela MA (2015) Ag2 and Ag3 clusters: synthesis, characterization, and interaction with DNA. Angew Chem Int Ed 54:7612–7616View ArticleGoogle Scholar
  7. Van der Linden M, Barendregt A, van Bunningen AJ, Chin PTK, Thies-Weesie D, de Groot FMF, Meijerink A (2016) Characterisation, degradation and regeneration of luminescent Ag29 clusters in solution. Nano 8:19901–19909Google Scholar
  8. Hakkinen H, Moseler M, Landman U (2002) Bonding in Cu, Ag, and Au clusters: relativistic effects, trends, and surprises. Phys Rev Lett 89:033401View ArticleGoogle Scholar
  9. Radcliffe P, Przystawik A, Diederich T, Doppner T, Tiggesbaumker J, Meiwes-Broer KH (2004) Excited-state relaxation of Ag8 clusters embedded in helium droplets. Phys Rev Lett 92:173403View ArticleGoogle Scholar
  10. Ošťádal I, Kocan P, Sobotik P, Pudl J (2005) Direct observation of long-range assisted formation of Ag clusters on Si(111)7×7. Phys Rev Lett 95:146101View ArticleGoogle Scholar
  11. Gao JF, Zhao JJ (2012) Initial geometries, interaction mechanism and high stability of silicene on Ag(111) surface. Sci Rep 2:861View ArticleGoogle Scholar
  12. CL D, Wang BB, Sun F, Huang ML, He CJ, Liu YW, Zhang XJ, Shi DN (2015) Refractive index sensitivities of plane Ag nanosphere cluster sensors. Sensor Actuat B-Chem 215:142–145View ArticleGoogle Scholar
  13. Petty JT, Sergev OO, Ganguly M, Rankine IJ, Chevrier DM, Zhang P (2016) A segregated, partially oxidized, and compact Ag10 cluster within an encapsulating DNA host. J Am Chem Soc 138:3469–3477View ArticleGoogle Scholar
  14. DK H, He X, Sun LF, GC X, Jiao LY, Zhao L (2016) Growth of single-walled carbon nanotubes from Ag15 cluster catalysts. Sci Bull 61:917–920View ArticleGoogle Scholar
  15. McKee ML, Samokhvalov A (2017) Density functional study of neutral and charged silver clusters Agn with n=2-22 evolution of properties and structure. J Phys Chem A 121:5018–5028View ArticleGoogle Scholar
  16. Feng DL, Feng YH, Yuan SW, Zhang XX, Wang G (2017) Melting behavior of Ag nanoparticles and their clusters. Appl Therm Eng 111:1457–1463View ArticleGoogle Scholar
  17. Kahlal S, Liu CW, Saillard JY (2017) Ag13-centered cuboctahedral architecture in inorganic cluster chemistry: a DFT investigation. Inorg Chem 56:1209–1215View ArticleGoogle Scholar
  18. Chen ZW, Wen Z, Jiang Q (2017) Rational design of ag38 cluster supported by graphdiyne for catalytic CO oxidation. J Phys Chem C 121:3463–3468View ArticleGoogle Scholar
  19. Chen PT, Tyo EC, Hayashi M, Pellin MJ, Safonova O, Nachtegaal M, van Bokhoven JA, Vajda S, Zapol P (2017) Size-selective reactivity of subnanometer Ag4 and Ag16 clusters on a TiO2 surface. J Phys Chem C 121:6614–6625View ArticleGoogle Scholar
  20. Liao MS, Watts JD, Huang MJ (2014) Theoretical comparative study of oxygen adsorption on neutral and anionic Agn and Aun clusters (n=2-25). J Phys Chem C 118:21911–21927View ArticleGoogle Scholar
  21. Zhang CX, Chen CH, Dong HX, Shen JR, Dau H, Zhao JQ (2015) A synthetic Mn4Ca-cluster mimicking the oxygen-evolving center of photosynthesis. Science 348:690–693View ArticleGoogle Scholar
  22. Hadipour NL, Peyghan AA, Soleymanabadi H (2015) Theoretical study on the Al-doped ZnO nanoclusters for CO chemical sensors. J Phys Chem C 119:6398–6404View ArticleGoogle Scholar
  23. Chi YH, Zhao LM, XQ L, An CH, Guo WY, CML W (2016) Effect of alloying on the stabilities and catalytic properties of Ag-Au bimetallic subnanoclusters: a theoretical investigation. J Mater Sci 51:5046–5060View ArticleGoogle Scholar
  24. Kahnouji H, Najafvandzadeh H, Hashemifar SJ, Alaei M, Akbarzadeh H (2015) Density-functional study of the pure and palladium doped small copper and silver clusters. Chem Phys Lett 630:101–105View ArticleGoogle Scholar
  25. Zhao YR, Zhang HR, Zhang MG, Zheng BB, Kuang XY (2014) DFT study of size-dependent geometries, stabilities and electronic properties of Si2Agn clusters: comparison with pure silver clusters. Mol Phys 112:972–981View ArticleGoogle Scholar
  26. Li YJ, Lyon JT, Woodham AP, Fielicke A, Janssens E (2014) The geometric structure of silver-doped silicon clusters. ChemPhysChem 15:328–336View ArticleGoogle Scholar
  27. Wang HQ, Kuang XY, Li HF (2009) Structural, electronic, and magnetic properties of gold cluster anions doped with zinc: AunZn- (2≤ n≤10) J Phys Chem A 113:14022-14028Google Scholar
  28. Xia XX, Kuang XY, Lu C, Jin YY, Xing XD, Merino G, Hermann A (2016) Deciphering the structural evolution and electronic properties of magnesium clusters: an aromatic homonuclear metal Mg17 cluster. J Phys Chem A 120:7947–7954View ArticleGoogle Scholar
  29. Gao Y, Liu XZ, Wang ZG (2017) Ce@Au14: a bimetallic superatom cluster with 18-electron rule. J Electron Mater 46:3899–3903View ArticleGoogle Scholar
  30. Hirsch K, Zamudio-Bayer V, Langenberg A, Niemeyer M, Langbehn B, Moller T, Terasaki A, von Issendorff B, Lau JT (2015) Magnetic moments of chromium-doped gold clusters: the anderson impurity model in finite systems. Phys Rev Lett 114:087202View ArticleGoogle Scholar
  31. Wang HQ, Li HF (2014) A combined stochastic search and density functional theory study on the neutral and charged silicon-based clusters MSi6 (M=La, Ce, Yb and Lu). RSC Adv 4:29782–29793View ArticleGoogle Scholar
  32. Ghanty TK, Banerjee A, Chakrabarti A (2010) A structures and the electronic properties of Au19X clusters (X=Li, Na, K, Rb, Cs, Cu, and Ag). J Phys Chem C 114:20–27View ArticleGoogle Scholar
  33. Joshi K, Krishnamurty S (2017) Thermo-stimuli response of doped MAun clusters (n=4-8; M=Si, Ge) at discrete temperatures: a BOMD undertaking. J Phys Chem C 121:17514–17522View ArticleGoogle Scholar
  34. Jaiswal S, Kumar V (2015) Growth behavior and electronic structure of neutral and anion ZrGen (n=1–21) clusters. Comput Theor Chem 1075:87–97View ArticleGoogle Scholar
  35. Kwak K, Tang Q, Kim M, Jiang DE, Lee D (2015) Interconversion between superatomic 6-electron and 8-electron configurations of M@Au24(SR)18 clusters (M=Pd, Pt). J Am Chem Soc 137:10833–10840View ArticleGoogle Scholar
  36. Zeng WP, Tang J, Wang P, Pei Y (2016) Density functional theory (DFT) studies of CO oxidation reaction on M13 and Au18M clusters (M=Au, Ag, Cu, Pt and Pd): the role of co-adsorbed CO molecule. RSC Adv 6:55867–55877View ArticleGoogle Scholar
  37. Xing XD, Hermann A, Kuang XY, Ju M, Lu C, Jin YY, Xia XX, Maroulis G (2015) Insights into the geometries, electronic and magnetic properties of neutral and charged palladium clusters. Sci Rep 6:19656View ArticleGoogle Scholar
  38. Xia XX, Hermann A, Kuang XY, Jin YY, Lu C, Xing XD (2016) Study of the structural and electronic properties of neutral and charged niobium-doped silicon clusters: niobium encapsulated in silicon cages. J Phys Chem C 120:677–684View ArticleGoogle Scholar
  39. Jin YY, Tian YH, Kuang XY, Zhang CZ, Lu C, Wang JJ, Lv J, Ding LP, Ju M (2015) Ab initio search for global minimum structures of pure and boron doped silver clusters. J Phys Chem A 119:6738–6745View ArticleGoogle Scholar
  40. Jin YY, Maroulis G, Kuang XY, Ding LP, Lu C, Wang JJ, Lv J, Zhang CZ, Ju M (2015) Geometries, stabilities and fragmental channels of neutral and charged sulfur clusters: Sn Q (n=3–20, Q =0, ±1). Phys Chem Chem Phys 17:13590View ArticleGoogle Scholar
  41. Ju M, Lv J, Kuang XY, Ding LP, Lu C, Wang JJ, Jin YY, Maroulis G (2015) Systematic theoretical investigation of geometries, stabilities and magnetic properties of iron oxide clusters (FeO)n μ (n=1–8, μ=0, ±1): insights and perspectives. RSC Adv 5:6560View ArticleGoogle Scholar
  42. Wang HQ, Kuang XY, Li HF (2010) Density functional study of structural and electronic properties of bimetallic copper-gold clusters: comparison with pure and doped gold clusters. Phys Chem Chem Phys 2:5156View ArticleGoogle Scholar
  43. Wang HQ, Li HF (2015) Structure identification of endohedral golden cage nanoclusters. RSC Adv 5:94685–94693View ArticleGoogle Scholar
  44. Li HF, Wang HQ (2014) Probing the stability of neutral and anionic transition-metal-doped golden cage nanoclusters: M@Au16 (M=Sc, Ti, V). Phys Chem Chem Phys 16:244–254View ArticleGoogle Scholar
  45. Mokkath JH, Schwingenschlogl U (2014) Structural and optical properties of Si-doped Ag clusters. J Phys Chem C 118:4885–4889View ArticleGoogle Scholar
  46. Zhao GF, Sun JM, Zeng Z (2007) Absorption spectra and electronic structures of AumAgn (m+n=8) clusters. Chem Phys 342:267–274View ArticleGoogle Scholar
  47. Li WY, Chen FY (2015) Alloying effect on performances of bimetallic Ag–Au cluster sensitized solar cells. J Alloy Compd 632:845–848View ArticleGoogle Scholar
  48. Chang L, HX X, Cheng DJ (2014) Role of ligand type on the geometric and electronic properties of Ag–Au bimetallic clusters. Comput Theor Chem 1045:35–40View ArticleGoogle Scholar
  49. Zhang N, Chen FY, XQ W (2015) Global optimization and oxygen dissociation on polyicosahedral Ag32Cu6 core-shell cluster for alkaline fuel cells. Sci Rep 5:11984View ArticleGoogle Scholar
  50. Ma WQ, Chen FY (2012) Optical and electronic properties of Cu doped Ag clusters. J Alloy Compd 541:79–83View ArticleGoogle Scholar
  51. Zhang YX, Yang ZX (2015) Tuning the catalytic activity of Ag-Pd alloy cluster for hydrogen dissociation by controlling the Pd ratio. Comput Theor Chem 1071:39–45View ArticleGoogle Scholar
  52. Sargolzaei M, Lotfizadeh N (2011) Spin and orbital magnetism of a single 3d transition-metal atom doped into icosahedral coinage-metal clusters X12 (X=Cu, Ag, Au). Phys Rev B 83:155404View ArticleGoogle Scholar
  53. Palagin D, Doye JPK (2016) DNA-stabilized Ag-Au bimetallic clusters: the effects of alloying and embedding on optical properties. Phys Chem Chem Phys 18:22311View ArticleGoogle Scholar
  54. Zhao S, Ren YL, WW L, Wang JJ, Yin WP (2012) Density functional study of H2S binding on small cationic AgnAum + (n+m≤5) clusters. Comput Theor Chem 997:70–76View ArticleGoogle Scholar
  55. Hussain R, Hussain AI, Chatha SAS, Mansha A, Ayu K (2017) Density functional theory study of geometric and electronic properties of full range of bimetallic AgnYm (n+m=10) clusters. J Alloy Compd 705:232–246View ArticleGoogle Scholar
  56. Zhang M, XY G, Zhang WL, Zhao LN, He LM, Luo YH (2010) Probing the magnetic and structural properties of the 3d, 4d, 5d impurities encapsulated in an icosahedral Ag12 cage. Physica B 405:642–648View ArticleGoogle Scholar
  57. Chen L, Wang ZG, Li ZQ, Zhang RQ (2017) Chemical coupling sers properties of pyridine on silver-caged metal clusters M@Ag12 (M = V, Nb, Ta, Cr, Mo, W, Mn+, Tc+, Re+). J Electron Mater 46:3904–3909View ArticleGoogle Scholar
  58. Medel VM, Reber AC, Chauhan V, Sen P, Koster AM, Calaminici P, Khanna SN (2014) Nature of valence transition and spin moment in AgnV+ clusters. J Am Chem Soc 136:8229–8236View ArticleGoogle Scholar
  59. Gong XY, WW J, Li TW, Feng ZJ, Wang Y (2015) Spin–orbit splitting and magnetism of icosahedral M@Ag12 clusters (M =3d and 4d atoms). J Clust Sci 26:759–773View ArticleGoogle Scholar
  60. Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA, Cheeseman JR, Montgomery JA, Jr Vreven T, Kudin KN, Burant JC et al (2009) Gaussian 09 revision a 02. Gaussian Inc, Wallingford CTGoogle Scholar
  61. Perdew JP, Chevary JA, Vosko SH, Jackson KA, Pederson MR, Singh DJ, Fiolhais C (1992) Atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation. Phys Rev B 46:6671–6687View ArticleGoogle Scholar
  62. Hay PJ, Wadt WR (1985) Ab initio effective core potentials for molecular calculations potentials for K to Au including the outermost core orbitals. J Chem Phys 82:299–311View ArticleGoogle Scholar
  63. Wang Y, Lv J, Zhu L, Ma Y (2010) Crystal structure prediction via particle-swarm optimization. Phys Rev B 82:094116View ArticleGoogle Scholar
  64. Janssens E, Neukermans S, Wang X, Veldeman N, Silverans RE, Lievens P (2005) Stability patterns of transition metal doped silver clusters: dopant- and size-dependent electron delocalization. Eur Phys J D 34:23–27View ArticleGoogle Scholar
  65. Janssens E, Neukermans S, Nguyen HMT, Nguyen MT, Lievens P (2005) Quenching of the magnetic moment of a transition metal dopant in silver clusters. Phys Rev Lett 94:113401View ArticleGoogle Scholar
  66. Reed AE, Curtiss LA, Weinhold F (1988) Intermolecular interactions from a natural bond orbital, donor-acceptor viewpoint. Chem Rev 88:899–926View ArticleGoogle Scholar
  67. Lee HM, Ge MF, Sahu BR, Tarakeshwar P, Kim KS (2003) Geometrical and electronic structures of gold, silver, and gold-silver binary clusters: origins of ductility of gold and gold-silver alloy formation. J Phys Chem B 107:9994–10005View ArticleGoogle Scholar
  68. Wu X, Ray AK (1999) A density functional study of small neutral and cationic vanadium clusters Vn and Vn + (n=2–9). J Chem Phys 110:2437View ArticleGoogle Scholar

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