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 Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （n = 1-8） clustersDensity functional theory study of Mg2Nin （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 Mg2Ni6 clusters 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.     

Hydrogen storage capabilities of the most stable isomers of NanBm (m+n=6) clusters

The most stable isomers of NanBm(m+n=6) clusters and their hydrogen storage properties are investigated by means of density functional theory with a 6-311+G(d) basis set. To study the hydrogen storage properties,all of the stable structures of Na n BmHx (m+n=6) clusters have been optimized. It shows that boron atoms of Na n B m are separated from the other boron atoms,and form satellite BHx (x=3,4) clusters around the centre,which attach to the system by a bridging bond of a hydrogen atom or an Na atom. Compared with the hydrogen storage capabilities,the Na3B3 has the highest hydrogen storage capacity among Na n B m clusters. The binding energies,interaction energies of hydrogen atom with Na n B m clusters and second difference in energy of Na3B3Hx clusters have been calculated. The results show that the stability of the Na n B m H x clusters present an odd-even oscillatory effect,as the number of H atoms increases.     

Geometries, stabilities, and electronic properties of Be-doped gold clusters: a density functional theory study

We have systematically investigated the geometrical structures, relative stabilities and electronic properties of small bimetallic AunBe (n = 1, 2, . . . , 8) clusters using a density functional method at BP86 level. The optimized geometries reveal that the impurity beryllium atom dramatically affects the structures of the Aun clusters. The averaged binding energies, fragmentation energies, second-order difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps and chemical hardness are investigated. All of them exhibit a pronounced odd-even alternation, manifesting that the clusters with even number of gold atoms possess relatively higher stabilities. Especially, the linear Au2Be cluster is magic cluster with the most stable chemical stability. According to the natural population analysis, it is found that charge-transferring direction between Au atom and Be atom changes at the size of n = 4.     

Density functional theory study on Ni-doped MgnNi (n=1-7) clusters

The possible geometrical and the electronic structures of small MgnNi(n = 1-7) clusters are optimised by the density functional theory with a LANL2DZ basis set.The binding energy,the energy gap,the electron affinity,the dissociation energy and the second difference in energy are calculated and discussed.The properties of Mg n Ni clusters are also discussed when the number of Mg atom increases.     

A density-functional theory for (BAs)n clusters (n=1 14): structures, stabilities and electronic properties

This paper investigates the lowest-energy structures,stabilities and electronic properties of (BAs) n clusters (n=1-14) by means of the density-functional theory.The results show that the lowest-energy structures undergo a structural change from two-dimensional to three-dimensional when n=4.With the increase of the cluster size (n 6),the (BAs) n clusters tend to adopt cage-like structures,which can be considered as being built from B 2 As 2 and six-membered rings with B-As bond alternative arrangement.The binding energy per atom,second-order energy differences,vertical electron affinity and vertical ionization potential are calculated and discussed.The caculated HOMO-LUMO gaps reveal that the clusters have typical semiconductor characteristics.The analysis of partial density of states suggests that there are strong covalence and molecular characteristics in the clusters.     

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.     

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.     

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.     

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

The equilibrium geometries,relative stabilities,and electronic properties of Mn Agm(M=Na,Li;n + m ≤ 7) as well as pure Ag n,Na n,Li n(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 Ag n,Na n,and Li n 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 Na n Ag m and Li n Ag m clusters.When n + m ≥ 5,a striking feature is that the trigonal bipyramid becomes the main subunit of Li n Ag m.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.     

An ab initio study of niobium (n = 2--11) clusters: structure, stability and magnetism

The ground-state configurations of the Nbn (n = 2-11) clusters are studied through the first-principles calculations. It is found that niobium clusters (n = 2-11) tend to form compact structures with low symmetry. The clusters with 4, 8 and 10 atoms are found to be magic and have relatively large highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gaps. The Nbn clusters possess low magnetic moments, which exhibit an odd-even oscillational character. The analyses of calculated electronic density and population of the lowest-energy niobium clusters for n = 2, 3, 5, 7, 9, 11 show that the total magnetic moments of Nbn originate mainly from a few Nb atoms with longer spacings between them in most cases, while they are located on two Nb atoms for n = 2, 3, 5. The total magnetic moments come mainly from the 4d local moments but with the exception of the Nb5 cluster.     

Electronic Structure of One—Dimensional Boron Chains with Density Functional Theory Method

One-dimensional chain structures of Bn(n=6-16) are calculated by employing a 6-311 G^* basis set.The present calculations show that all the chain structures of interest have local minima with large binding energy per atom and short bond length.It is also found that many previous reported structures of B6 and B7 clusters are saddle points and the one-dimensional chain structures are the corresponding ground-state structures of B6 and B7 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.     

Structures of Adatom Clusters on Ag（111） Surface by Genetic Algorithm

We study the structures of Ag adatom clusters supported on the metal Ag(111) surface using the genetic algorithm (GA). The atomic interactions are modelled by the surface-embedded-atom method. The lowest-energy structures of adatom clusters with sizes n=3-20 are obtained, in which n=7, 10, 12, 14, 16, 19 are the magic numbers. Furthermore, we give a series of structures with energies close to the lowest energy (the lower-energy isomers), and the structure features are studied in detail. Except for some magic clusters and small clusters, every configuration of adatom clusters generally has two distinct adsorption ways, so the isomers always appear in pairs.     

Structure and magnetic properties of Osn （n=11～22） clusters

The structure and magnetic properties of Osn （n=11～22） clusters are systematically studied by using density functional theory （DFT）. For each size, the average binding energy per atom, the second-order differences of total energies and the highest occupied molecular orbital （HOMO）–the lowest unoccupied molecular orbital （LUMO） gaps are calculated to analyze the stability of the cluster. The structures of Os14 and Os18 clusters are based on a close-packed hexagonal structure, and they have maximum stabilities, so n=14, 18 are the magic numbers. The 5d electrons play a dominant role in the chemical reaction of Osn clusters. The magnetic moments of Osn clusters are quenched around n=12, and when n=18～22 the value approximates to zero, due to the difference of electron transfer.     

First-principles study of structures and electronic properties of cadmium sulfide clusters

The lowest-energy structures and the electronic properties of CdnSn （n = 1 - 8） clusters have been studied by using denslty-functional theory simulating package DMol^3 in the generalized gradient approximation （GGA）. The ring-like structures are the lowest-energy configurations for n = 2, 3 and the three-dimensional spheroid configurations for n = 4 - 8. The three-dimensional structures may be considered as being built from the Cd2S2 and Cd3S3 rings. Compared to the previous reports, we have found the more stable structures for CdnSn（n = 7, 8）. Calculations show that the magic numbers of CdnSn （n = 1-8） clusters are n = 3 and 6. As cluster size increases, the properties of CdnSn clusters tend to bulk-like ones in binding energy per CdS unit and Mulliken atomic charge, obtained by comparing with the calculated results of the wurtzite and zinc blende CdS for the same simulating parameters.     

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.     

Density functional study of AunCu (n=1-7) clusters

The possible stable geometrical configurations and the relative stabilities of the lowest-lying isomers of copper-doped gold clusters,Au n Cu (n=1-7),are investigated using the density functional theory.Several low-lying isomers are determined.The results indicate that the ground-state Au n Cu clusters have planar structures for n=1-7.The stability trend of the Au n Cu clusters (n=1-7),shows that odd-numbered Au n Cu clusters are more stable than the neighbouring even-numbered ones,thereby indicating the Au 5 Cu clusters are magic cluster with high chemical stability.     

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 B n Al (2 ≤ n ≤ 9) clusters are systematically investigated by using the first-principles density functional theory. The results show that the Al 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 B n Al (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 B 4 Al and B 8 Al clusters each have a higher relative stability. Especially, the B 8 Al cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced odd-even oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B 7 Al and B 9 Al clusters.     

Theoretical study of small Mo clusters and molecular nitrogen adsorption on Mo clusters

This paper studies the small molybdenum clusters of Mo_n (n=2--8) and their adsorption of N₂ molecule by using the density functional theory (DFT) with the generalized gradient approximation. The optimized structures of Mo_n clusters show the onset of a structural transition from a close-packed structure towards a body-centred cubic structure occurred at n=7. An analysis of adsorption energies suggests that the Mo₂ is of high inertness and Mo₆ cluster is of high activity against the adsorption of N₂. Calculated results indicate that the N₂ molecule prefers end-on mode by forming a linear or quasi-linear structure Mo--N--N, and the adsorption of nitrogen on molybdenum clusters is molecular adsorption with slightly elongated N--N bond. The electron density of highest occupied molecular orbital and lowest unoccupied molecular orbital, and the partial density of states of representative cluster are also used to characterize the adsorption properties of N₂ on the sized Mo_n clusters.