Density functional theory study of Mg_2Ni_n(n= 1–8) clusters

The density functional theory B3PW91 with LANL2DZ basis sets has been used to study the possible geometries of Mg2Nin(n = 1–8) clusters. For the lowest energy structures of the clusters, stabilities, electronic properties, and natural bond orbital(NBO) are calculated and discussed. The results show that the doped Mg atoms reduce the stabilities of pure Ni clusters. The Mg2Ni2, Mg2Ni4, and Mg2Ni6clusters are more stable than neighboring clusters. The system appears magic number characteristics. In addition, the hybridization phenomenon occurs, owing to the interaction of Mg and Ni. The result of charge transfer is that Ni atom is negative and the Mg atom is positive. We also conclude that the 3p and 4d orbitals of the Ni atom have an effect on the stabilities of the clusters.     

Density functional theory study of MgnNi2 （n=1-6） clusters

The geometries of Mg n Ni 2(n = 1-6) clusters are studied by using the hybrid density functional theory(B3LYP) with LANL2DZ basis sets.For the ground-state structures of Mg n Ni 2 clusters,the stabilities and the electronic properties are investigated.The results show that the groundstate structures and symmetries of Mg clusters change greatly due to the Ni atoms.The average binding energies have a growing tendency while the energy gaps have a declining tendency.In addition,the ionization energies exhibit an odd-even oscillation feature.We also conclude that n = 3,5 are the magic numbers of the Mg n Ni 2 clusters.The Mg 3 Ni 2 and Mg 5 Ni 2 clusters are more stable than neighbouring clusters,and the Mg 4 Ni 2 cluster exhibits a higher chemical activity.     

Density functional theory study of neutral AlS_n(n=2-9) clusters

This paper investigates the geometrical structures and relative stabilities of neutral AlS n(n = 2-9) using the density functional theory.Structural optimisation and frequency analysis are performed at the B3LYP/6-311G(d) level.The ground state structures of the AlS n show that the sulfur atoms prefer not only to evenly distribute on both sides of the aluminum atom but also to form stable structures in AlS n clusters.The structures of pure S n are fundamentally changed due to the doping of the Al atom.The fragmentation energies and the second-order energy differences are calculated and discussed.Among neutral AlS n(n = 2-9) clusters,AlS 4 and AlS 6 are the most stable.     

Structure,stability and electronic properties of SrSin （n ： 1-12） clusters： Density-functional theory investigationStructure,stability and electronic properties of SrSin （n ： 1-12） clusters： Density-functional theory investigation

Geometric structures, stabilities, and electronic properties of SrSin （n = 1-12） clusters have been investigated using the density-functional theory within the generalized gradient approximation. The optimized geometries indicate that one Si atom capped on SrSin_ 1 structure and Sr atom capped Sin structure for difference SrSin clusters in size are two dominant growth patterns. The calculated average binding energy, fragmentation energy, second-order energy difference, the highest occupied molecular orbital, and the lowest unoccupied molecular orbital （HOMO-LUMO） gaps show that the doping of Sr atom can enhance the chemical activity of the silicon framework. The relative stability of SrSi9 is the strongest among the SrSin clusters. According to the mulliken population and natural population analysis, it is found that the charge in SrSin clusters transfer from Sr atom to the Sin host. In addition, the vertical ionization potential, vertical electron affinity, and chemical hardness are also discussed and compared.     

Structures,stabilities, and electronic properties of F-doped Sin （n=1～12） clusters：Density functional theory investigation

The geometries, stabilities, and electronic properties of FSin （n=1～12） clusters are systematically investigated by using first-principles calculations based on the hybrid density-functional theory at the B3LYP/6-311G level. The geometries are found to undergo a structural change from two-dimensional to three-dimensional structure when the cluster size n equals 3. On the basis of the obtained lowest-energy geometries, the size dependencies of cluster properties, such as averaged binding energy, fragmentation energy, second-order energy difference, HOMO–LUMO （highest occupied molecular orbital–lowest unoccupied molecular orbital） gap and chemical hardness, are discussed. In addition, natural population analysis indicates that the F atom in the most stable FSin cluster is recorded as being negative and the charges always transfer from Si atoms to the F atom in the FSin clusters.     

First-principles calculations for titanium monoxide clusters TinO （n=1-9）

Based on the density-functional theory, this paper studies the geometric and magnetic properties of TinO （n=1-9） clusters. The resulting geometries show that the oxygen atom remains on the surface of clusters and does not change the geometry of Tin significantly. The binding energy, second-order energy differences with the size of clusters show that Ti7O cluster is endowed with special stability. The stability of TinO clusters is validated by the recent time-of-flight mass spectra. The total magnetic moments for TinO clusters with n=1-4, 8-9 are constant with 2 and drop to zero at n=5-7. The local magnetic moment and charge partition of each atom, and the density of states are discussed. The magnetic moment of the TinO is clearly dominated by the localized 3d electrons of Ti atoms while the oxygen atom contributes a very small amount of spin in TinO clusters.     

Unique Magnetic Moment and Electronic Properties for Fe（MgO）n（n=1-8） Clusters： First-Principles Calculations

The geometries and electronic properties of Fe（MgO）n are systematically investigated by the density functional theory. The results show that the doped Fe atom is prone to bond with the O atom, and Fe almost does not disturb the frame of （MgO）n. The second-order energy difference, the fragmentation energies and the electron amnities show that Fe（MgO）4 and Fe（MgO）6 possess relatively higher stabilities. The HOMO-LUMO gaps of Fe（MgO）n decrease obviously as compared with （MgO）n. Almost equal unpaired electrons of the 3d state of the Fe atom in Fe（MgO）n result in a nearly equal magnetic moment of Fe（MgO）n.     

A density functional theoretical investigation of RhSin（n = 1-6） clusters

This paper computationally investigates the RhSin （n = 1 6） clusters by using a density functional approach. Geometry optimizations of the RhSin （n = 1 6） clusters are carried out at the B3LYP level employing LanL2DZ basis sets. It presents and discusses the equilibrium geometries of the RhSin （n = 1-6） clusters as well as the corresponding averaged binding energies, fragmentation energies, natural populations, magnetic properties, and the energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. Theoretical results show that the most stable RhSin（n = 1-6） isomers keep an analogous framework of the corresponding Sin＋1 clusters, the RhSi3 is the most stable cluster in RhSin （n = 1-6） isomers. Furthermore, the charges of the lowest-energy RhSin （n = 1-6） clusters transfer mainly from Si atom to Rh atom. Meanwhile, the magnetic moments of the RhSin（n = 1-6） arises from the 4d orbits of Rh atom. Finally, compared with the Sin＋1 cluster, the chemical stability RhSin clusters are universally improved.     

First-principles study on the structure,electronic and magnetic properties of HoSin （n=1-12, 20） clusters

The structure, electronic and magnetic properties of HoSin（n= 1 - 12, 20） clusters have been widely investigated by first-principles calculation method based on density flmctional theory （DFT）. From our calculation results, we find that for HoSin（n=1- 12） clusters except n = 7.10, the most stable structures are a replacement of Si atom in the corresponding pure Sin＋1 clusters by Ho atom. The doping of Ho atom makes the stability of Si clusters enhance remarkably, and HoSin（n = 2, 5, 8, 11） clusters are more stable than their neighboring clusters. The magnetic moment of Ho atom in HoSin （n = 1 - 12, 20） clusters mainly comes from of electron of tto, and never quenches.     

A density functional theory structures,stabilities, and study on size-dependent electronic properties of bimetallic MnAgm （M=Na,Li; n ＋ m ≤ 7） clusters

The equilibrium geometries, relative stabilities, and electronic properties of MnAgm（M=Na, Li; n ＋ m ≤ 7） as well as pure Agn, Nan, Lin （n ≤ 7） clusters are systematically investigated by means of the density functional theory. The optimized geometries reveal that for 2 ≤ n ≤ 7, there are significant similarities in geometry among pure Agn, Nan, and Lin clusters, and the transitions from planar to three-dimensional configurations occur at n = 7, 7, and 6, respectively. In contrast, the first three-dimensional （3D） structures are observed at n ＋ m = 5 for both NanAgm and LinAgm clusters. When n ＋ m ≥5, a striking feature is that the trigonal bipyramid becomes the main subunit of LinAgm. Furthermore, dramatic odd-even alternative behaviours are obtained in the fragmentation energies, secondorder difference energies, highest occupied and lowest unoccupied molecular orbital energy gaps, and chemical hardness for both pure and doped clusters. The analytic results exhibit that clusters with an even electronic configuration （2, 4, 6） possess the weakest chemical reactivity and more enhanced stability.     

A comparative study on geometries,stabilities, and electronic properties between bimetallic AgnX（X=Au,Cu;n=1-8）and pure silver clusters

Using the meta-generalized gradient approximation (meta-GGA) exchange correlation TPSS functional, the geo- metric structures, the relative stabilities, and the electronic properties of bimetallic Ag n X (X=Au, Cu; n=1–8) clusters are systematically investigated and compared with those of pure silver clusters. The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n = 6 for the Ag n Au clusters, and at n = 5 for Ag n Cu clusters. For different-sized Ag n X clusters, one X (X=Au or Cu) atom substituted Ag n+1 structure is a dominant growth pattern. The calculated fragmentation energies, second-order differences in energies, and the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) energy gaps show interesting odd–even oscillation behaviours, indicating that Ag 2,4,6,8 and Ag 1,3,5,7 X (X=Au, Cu) clusters keep high stabilities in comparison with their neighbouring clusters. The natural population analysis reveals that the charges transfer from the Ag n host to the impurity atom except for the Ag 2 Cu cluster. Moreover, vertical ionization potential (VIP), vertical electronic affinity (VEA), and chemical hardness (η) are discussed and compared in depth. The same odd–even oscillations are found for the VIP and η of the Ag n X (X=Au, Cu; n=1–8) clusters.     

First-Principles Study of Geometries,Stabilities and Electronic Properties of Ca2Sin （n=1-11） Clusters

The equilibrium geometries, relative stabilities, and electronic properties of Ca2Sin （n = 1-11） clusters have been systematically investigated by using the density function theory at the 6-311G （d） level The optimized geometries indicate that the most stable isomers have three-dimensional structures for n = 3-11. The electronic properties of Ca2 Sin （n = 1-11） dusters axe obtained through the analysis of the natural charge population, natural electron configuration, vertical ionization potential, and vertical electron affinity. The results show that the charges in corresponding Ca2Sin clusters transfer from the Ca atoms to the Sin host. Based on the obtained lowest-energy geometries, the size dependence of cluster properties, such as averaged binding energies, fragmentation energies, second-order energy differences, HOMO- LUMO gaps and chemical hardness, are deeply discussed.     

First Principle Calculation on AunAg2 （n = 1 - 4） Clusters

The first-principles method based on density-functional theory is used to investigate the geometries of the lowest-lying isomers of AunAg2 （n = 1 - 4） clusters. Several low-lying isomers are determined, and many of them in electronic configurations with a high spin multiplicity. The stability trend of Ag-doped Aun dusters is compared to that of pure Aun clusters. Our results indicate that the inclusion of two Ag atoms in the clusters lowers the cluster stability, indicating higher stability as the structures grow in size. The bigger energy difference between the Aun and AunAg2 curves as the structures grows in size. This information will be useful to understanding the enhanced catalytic activity and selectivity gained by using silver-doped gold catalyst.     

Structure,stability and electronic properties of SrSi_n(n= 1–12) clusters::Density-functional theory investigation

Geometric structures, stabilities, and electronic properties of SrSin(n = 1–12) clusters have been investigated using the density-functional theory within the generalized gradient approximation. The optimized geometries indicate that one Si atom capped on SrSin 1structure and Sr atom capped Sinstructure for difference SrSinclusters in size are two dominant growth patterns. The calculated average binding energy, fragmentation energy, second-order energy difference, the highest occupied molecular orbital, and the lowest unoccupied molecular orbital(HOMO–LUMO) gaps show that the doping of Sr atom can enhance the chemical activity of the silicon framework. The relative stability of SrSi9is the strongest among the SrSinclusters. According to the mulliken population and natural population analysis, it is found that the charge in SrSin clusters transfer from Sr atom to the Sinhost. In addition, the vertical ionization potential, vertical electron affinity, and chemical hardness are also discussed and compared.     

Quantum-Mechanical Study of Small Au2Pdn （n=1 ～ 4） Clusters

Gold-doped palladium clusters, Au2Pdn （n=1～4）, are investigated using the density functional method B3LYP with relativistic effective core potentials （RECP） and LANL2DZ basis set. The possible geometrical configurations with their electronic states are determined, and the stability trend is investigated. Several low-lying isomers are determined, and many of them are in electronic configurations with a high-spin multiplicity. Our results indicate that the palladium-gold interaction is strong enough to modify the known pattern of bare palladium clusters, and the lower stability as the structures grow in size. The present calculations are useful to understanding the enhanced catalytic activity and selectivity gained by using gold-doped palladium catalyst.     

Equilibrium geometries and electronic properties of BenLi （n=2-15） clusters from first principles

This paper studies the equilibrium geometries and electronic properties of Ben and BenLi clusters, up to n=15, by using density-functional theory（DFT） at B3LYP/6-31G（d） level. The lowest-energy structures of Ben and BenLi clusters were determined. The results indicate that a single lithium impurity enhances the stability and chemical reactivity of the beryllium clusters. It finds that the geometries of the host clusters change significantly after the addition of the lithium atom for n ≥8. The lithium impurity prefers to be on the periphery of beryllium clusters, and occupies vertex sites. Both Be4Li, Be9Li, and Be13Li were found to be particularly stable with higher average binding energy, local peaks of second-order energy difference and fragmentation energies. For all the BenLi clusters studied, we found charge transfers from the Li to Be site and co-existence of covalent and metallic bonding characteristics.     

Photoabsorption Spectra of （SiO2）n （n ≤ 5） Clusters on the Basis of Time-Dependent Density Functional Theory

The photoabsorption spectra of （SiO2）n （n = 2-5） clusters [including isomers （D3h, D2d） structures of （SiO2）3 and （C2v, D2h, D4h） structures of （SiO2）4] are calculated by using time-dependent density-function theory. The equilibrium geometries, the binding energy, the gap between the highest occupied and lowest unoccupied molecular orbitals and vertical ionization potential for corresponding structures are computed using several methods with different types of the basis functions. It is found that the polarizability functions are necessary for the basis functions when optimize the structures of silicon oxide clusters. For different geometries of various clusters and the related isomers, their spectra are very different. Meanwhile, the comparison between using local-density generalized-gradient approximations for exchange-correlation potentials shows that both the calculated spectra present the same spectral feature. We suggest that the calculated photoabsorption spectra could be taken as a tool to elucidate the isomers and dusters structure.     

Structures and electronic properties of Mo2nNn（n=1-5）:a density functional study

The lowest-energy structures and the electronic properties of Mo2nNn(n=1-5) clusters have been studied by using the density functional theory(DFT) simulating package DMol 3 in the generalized gradient approximation(GGA).The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mo n(n = 2,4,6,8,10) clusters and nitrogen atoms which surround these cores.The average binding energy,the adiabatic electron affinity(AEA),the vertical electron affinity(VEA),the adiabatic ionization potential(AIP) and the vertical ionization potential(VIP) of Mo2nNn(n=1-5) clusters have been estimated.The HOMO-LUMO gaps reveal that the clusters have strong chemical activities.An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.     

Structural,electronic, and magnetic properties of boron cluster anions doped with aluminum：BnAl-（2〈n〈9）

The geometrical structures, relative stabilities, electronic and magnetic properties of small BnAl-（2〈n〈9）clusters are systematicalyy investigated by using the first-principles density functional theory. The results show that the A1 atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable BnAl-（2〈n〈9） isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4A1- and B8A1- clusters each have a higher relative stability. Especially, the BsA1-cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B7A1- and BgA1- clusters.     

A density functional theory study on the adsorption of CO and O2 on Cu-terminated Cu2O （111） surface

The adsorptions of CO and 02 molecules individually on the stoichiometric Cu-terminatcd Cu20 （111） surface are investigated by first-principles calculations on the basis of the density functional theory. The calculated results indicate that the CO molecule preferably coordinates to the Cu2 site through its C atom with an adsorption energy of-1.69 eV, whereas the 02 molecule is most stably adsorbed in a tilt type with one O atom coordinating to the Cu2 site and the other O atom coordinating to the Cul site, and has an adsorption energy of -1.97 eV. From the analysis of density of states, it is observed that Cu 3d transfers electrons to 2π orbital of the CO molecule and the highest occupied 5σ orbital of the CO molecule transfers electrons to the substrate. The sharp band of Cu 4s is delocalized when compared to that before the CO molecule adsorption, and overlaps substantially with bands of the adsorbed CO molecule. There is a broadening of the 2π orbital of the 02 molecule because of its overlapping with the Cu 3d orbital, indicating that strong 3d-2π interactions are involved in the chemisorption of the 02 molecule on the surface.