Theoretical Study on the Structures and Thermal Properties of Ag–Pt–Ni Trimetallic Clusters

The structures and thermal properties of Ag–Pt–Ni ternary nanoclusters varying with different compositions and sizes are studied by Monte Carlo and molecular dynamics simulations. It can be found that silver atoms tend to occupy the surface and platinum atoms favor the subsurface occupation, whereas the inner is occupied by nickel atoms due to the different surface energies and lattice parameters. In addition, there is a non-monotonous relationship between the melting points and compositions of Ag–Pt–Ni ternary nanoclusters according to molecular dynamics simulations. In addition, a linear decrease in melting point with \(N^{ - 1/3}\) is found for both monometallic and trimetallic clusters. This behavior is consistent with Pawlow’s law.     

Study of Structures and Electronic Properties of Pdn-1Pb and Pdn(n≤8) Clusters

Geometric and electronic properties of Pdn-1Pb and Pdn(n≤8) clusters have been studied by using density functional theory with effective core potentials, focusing on the differences between mono- and bimetallic clusters. The average bond length of Pdn-1Pb (n≤8) bimetallic clusters is longer than that of pure palladium clusters except for n = 2 and 3. The most stable structure of Pdn-1Pb (n≤7) is the singlet where there is at least a Pd or Pb atom on its excited state. The energy gaps of Pd-Pb binary clusters are narrower than those of Pdn clusters, and then the chemical activity is strengthened when Pdn clusters are doped with Pb.     

Structures and Electronic Properties of Ni–Al Alloy Clusters from First-Principles Calculations

Using the density functional theory calculations with the PBE exchange–correlation energy functional, we have studied the low-energy structures and electronic properties of Ni–Al alloy clusters for adsorbing or doping an aluminum atom to Ni_n (n = 13, 19, 23, 26, 29 and 55) clusters. The most stable structures of Ni_nAl are viewed as adding an Al atom at the hollow triangle and rhombus site of the icosahedron (n = 13, 55) and double-icosahedron (n = 19, 23, 26 and 29) structures, respectively. For Ni_n?1Al, it can be seen that an Al atom gradually moves from surface (n = 13, 19, 23 and 26) to the interior site (n = 29, 55) in the most stable structures. The electronic properties of the Ni–Al alloy clusters including binding energies, magnetic properties, charge transfer and density of states have also been studied.     

Theoretical Study on the Electronic Structures of Small TinNm （n ＋ m = 5, 6） Clusters

45 isomers of TinNm （n ＋ m = 5, 6） clusters, including linear, some planar and some stero configurations, have been predicted by density functional theory method. For five-atom clusters Ti3N2 and Ti2N3, the most stable structures are trigonal bipyramid in D3h symmetry, and for TiaN cluster, the isomer with one nitrogen atom occupying the center of quasi-tetrahedron is the most stable. In the isomers of Ti4N2 and Ti3N3, the planar networks are more stable, but for Ti2N4, the six-membered ring configuration is the most favorable. Most linear structures can form weak-strong bonds alternately with higher energy. As regards to planar structures, the more Ti-N bonds are formed, the more stable they will be; for stero closed polyhedral isomers, their energies are lower.     

Theoretical Study of Electronic Structure and Stability of Mixed AlmBn−mH n 2− and CmBn−mH n 2−m (n = 6, 10, 12 and m = 1, 2) Clusters

Density functional theory (DFT) method with B3LYP functional and 6-311++G(d,p) basis set has been used to predict the geometries, relative stabilities, electronic structures and bonding analysis of Mixed Al_mB_n?mH _n ^2? and C_mB_n?mH _n ^2?m (n = 6, 10, 12 and m = 1, 2) clusters; being compared to the B_nH _n ^2? ones. Therefore, the DFT results suggest that the replacing of boron by aluminium or carbon is governed by Natural net charges following Gimar’s and Williams’s rules. The Al_mB_n?mH _n ^2? structures are relatively distorted compared to those of B_nH _n ^2? and C_mB_n?mH _n ^2?m . In Al_mB_n?mH _n ^2? structures Al atoms prefer the adjacent sites, however for the C₂B_n?2H_n cluster cages, the carbon atoms are positioned at diametrically opposed sites. The large HOMO–LUMO gaps show that the predicted clusters have chemical stabilities, principally, those of Al_mB_n?mH _n ^2? ones, which are not experimentally isolated. The optimized geometries obtained through boron substitution by Al and C lead to compactness and to contracted structures, respectively, where B–B bonds are the shortest in mono- and di-carbaboranes.     

Theoretical Study of the Structural,Electronic, and Magnetic Properties of Zirconium-doped Aluminum Clusters:Al_nZr(n = 1～14)

The geometrical structures, stabilities, electronic and magnetic properties of Al_nZr(n = 1~14) clusters have been systematically investigated using density functional theory. It is found that for the optimized clusters the zirconium atom prefers to remain on the surface, and the growth patterns are organized as follows: Zr substituted Al_(n+1) clusters or Zr capped Aln clusters as well as Al added Al_(n-1)Zr clusters. All doped clusters exhibit relatively larger average binding energies and magnetic behaviors compared with pure Al_(n+1) counterpart. The calculated fragmentation energies and second-order difference of energies exhibit pronounced odd-even alternation behavior as a function of the cluster size when n = 3~13. In all Al_nZr clusters, there exits internal hybridization in both Al and Zr atoms and charge transfer from Al to Zr atom, which reflects the strong interactions between the two kinds of atoms. The magnetic property analysis shows that the 4d electrons of Zr atom are the main origin for cluster magnetism.     

Quantum Chemistry Studies on the Difference of Structures and Electronic Properties of Polyacene,Polypyridinopyridine and Paracyanogen

IntroductionThestudiesonconductivepo1ymershavebeenofmuchinterestsbothinex-perimentalworkandtheorysincetheresultsonconductivityofdopedpolyacety-lenewerereported.Itwasreportedthatthehighestconductivityofdopedpoly-acetylenereachedupto1O5s/cmandjustfellintherangeofmetalconduction[1].Somepeoplehaveputforwardone-dimension(1D)graphitematerialfamilytobeconsistedofcondensedaromaticrings.Therearetwbkindsofimportantmolecularskeletonsforms,oneisanextended.versionfrompolyacene.Thepolyacenecanbeobtaintedb…     

Theoretical Studies on the Structures and Stabilities of Charged, Titanium-Doped, Small Silicon Clusters, TiSi n ? /TiSi n + (n?=?1–8)

The structures and stabilities of charged, titanium-doped, small silicon clusters TiSi _n ⁺ /TiSi _n ^? (n?=?1–8) have been systematically investigated using the density functional theory method at the B3LYP/6-311+G* level. For comparison, the geometries of neutral TiSi_n clusters were also optimized at the same level, although most of them have been reported previously (Guo et al., J Chem Phys 126: 234704, 2007). Our results indicate that all neutral TiSi_n clusters favor Si-capped TiSi_n?1 structures, with the lowest energy structure of TiSi₂, TiSi₃, TiSi₄, TiSi₅, TiSi₆, TiSi₇ and TiSi₈ being Si-side-on TiSi adduct, Si-face-capped TiSi₂ triangle, Si-face-capped TiSi₃ trigonal pyramid, Si-face-capped TiSi₄ trigonal bipyramid, Si-face-capped TiSi₅ square bipyramid, Si-face-capped TiSi₆ pentagonal bipyramid, and Si-face-capped TiSi₇ capped pentagonal bipyramid, respectively. The ground state structures obtained herein for the neutral TiSi_n clusters agree well with those of Guo et al. except for TiSi₃ and TiSi₈. Adding or removing an electron greatly changes some ground state structures, i.e. for TiSi₃ ^?/TiSi₃ ⁺, TiSi₅ ^?, TiSi₆ ^?/TiSi₆ ⁺ TiSi₇ ^? and TiSi₈ ^?/TiSi₈ ⁺; others are almost unchanged, e.g. TiSi₂ ^?/TiSi₂ ⁺, TiSi₄ ^?/TiSi₄ ⁺, TiSi₅ ⁺ and TiSi₇ ⁺. Based on the optimized geometries, various energetic properties, including binding energies, fragmentation energies, second-order difference energies, HOMO–LUMO energy gaps, ionization potentials and electron affinities, were calculated for all the most stable isomers. The average binding energies reveal that all of TiSi_n/TiSi _n ⁺ /TiSi _n ^? (n?=?1–8) clusters can continue to gain energy as the size increasing. The fragmentation energies and second-order energy differences suggest that neutral TiSi₅, anionic TiSi₅ ^? and cationic TiSi₆ ⁺ are relatively stable.     

Atomistic Structures,Stabilities, Electronic Properties,and Chemical Bonding of Boron–Aluminum Mixed Clusters B3Al n 0/−/+ (n = 2–6)

Journal of Cluster Science - Neutral, anionic, and cationic B3Al n 0/?/+ (n?=?2–6) clusters were systematically explored using density functional theory and coupled cluster...     

Nonorthogonal Tight-binding Study of the Geometries and Electronic Properties of Ge_n(n=2—20)Clusters

ＩｎｔｒｏｄｕｃｔｉｏｎＳｔｕｄｉｅｓｏｎｃｌｕｓｔｅｒｓｏｆｇｒｏｕｐⅣｅｌｅｍｅｎｔｓ（Ｃ,Ｓｉ,Ｇｅ,ＳｎａｎｄＰｂ）ｈａｖｅｒｅｃｅｉｖｅｄｍｕｃｈａｔｅｎｔｉｏｎｉｎｔｈｅｌａｓｔｄｅｃａｄｅｆｏｒｔｈｅｉｒｐｏｔｅｎｔｉａｌａｐｐｌｉｃａ...     

Theoretical Studies on the Structures and Reactions of Halocarbenoids(Ⅰ) Structures and Stability of

ＴｈｅｏｒｅｔｉｃａｌＳｔｕｄｉｅｓｏｎｔｈｅＳｔｒｕｃｔｕｒｅｓａｎｄＲｅａｃｔｉｏｎｓｏｆＨａｌｏｃａｒｂｅｎｏｉｄｓ（Ⅰ）ＳｔｒｕｃｔｕｒｅｓａｎｄＳｔａｂｉｌｉｔｙｏｆＣｈｌｏｒｏｃａｒｂｅｎｏｉｄＣＨＣｌ_２ＬｉＬＩＪｉ－ｈａｉ，ＦＥＮＧＳ?..     

Probing the Structures,Stabilities and Electronic Properties of Neutral and Anionic PrSinλ (n = 1–9, λ = 0, − 1) Clusters: Comparison with Pure Silicon Clusters

Journal of Cluster Science - Silicon-based clusters have attracted particular attention because they are regard as building blocks for developing silicon-based nanomaterials. However, pure silicon...     

Study of Structures and Electronic Properties of Pdn–1Pb and Pdn （n≤8） Clusters

Geometric and electronic properties of Pdn–1Pb and Pdn (n≤8) clusters have been studied by using density functional theory with effective core potentials, focusing on the differences between mono- and bimetallic clusters. The average bond length of Pdn–1Pb (n≤8) bimetallic clusters is longer than that of pure palladium clusters except for n = 2 and 3. The most stable structure of Pdn–1Pb (n≤7) is the singlet where there is at least a Pd or Pb atom on its excited state. The energy gaps of Pd–Pb binary clusters are narrower than those of Pdn clusters, and then the chemical activity is strengthened when Pdn clusters are doped with Pb.     

Theoretical Studies on the Structures and Reactions of Halocarbenoids(Ⅰ)Structures and Stability of Chlorocarbenoid CHCl2

The chlorocarbenoid, CHCl₂Li, was studied by means of ab initio molecular orbital theory. Three equilibrium structures and two isomerization transition states were located. The calculations showed that the three-membered ring structure is the most stable. The "classical tetrahedral" structure is not the local minimum on the potential energy surface.     

Comment on “Theoretical Investigations on Geometrical and Electronic Structures of Silver Clusters”

We would like to make a few comments on the results reported in a recent paper in this journal by Tsuneda, J. Comput. Chem, 2019, 40, 206. The structures of some pure silver clusters were not correctly assigned. © 2019 Wiley Periodicals, Inc.     

Studies on the Relationship Between Electronic Structures and Superconducting Properties of TlBaCaCuO, BiSrCaCuO and XBaCuO(X=Y, Nd,Dy) Systems

IntroductionUptonow,therehavebeenreportsonthemaintypicalhighcriticaltemper-aturesuperconducting(HTS)systems:BiSrCaCuO,T1BaCaCuOandXBaCuO(XdenotesheavyandraremetalssuchasY,Nd,Dy).IthasalsobeenreportedthatdopingPb,Mo,Al,W,Ti,SbandFetc.insuperconductorscanmaintainTc.Thestructuresareallioniccrystalswhicharecomposedofrare(orheavy)metalelementsandBaCuO,BaCaCuO(orSrCuO,SrCaCuO)components.Thecrystalce1lunitsofTlBaCaCuO,BiSrCaCuOandXBaCuO(X=Y,Nd,DY)su-perconductorsareshowninFi…     

Computational Studies on the Sc<Subscript>n</Subscript>N<Subscript>m</Subscript> (n + m=10) Clusters: Structure,Electronic and Vibrational Properties

Besides the size and structure, compositions also dramatically affect the properties of clusters. In fact, the increased degree of freedom poses much more challenges to determine the global minimum structure of multi-component clusters. In this thesis, based on the CALYPSO structure searching method, the global minimum structures are obtained for Sc_nN_m (n + m=10) clusters at PW91/6-311+G(d) level. The growth behavior indicates that the cage unit tends to arrange into the compact configurations, and the occupied positions of N atoms shift from the surface towards the center of coordination site with the increasing number of Sc atoms. The relative stabilities have been discussed by analyzing the average binding energies and HOMO–LUMO gaps. In addition, the molecular orbitals, dipole moments, polarizability, hyperpolarizabilities, natural population, natural electron configuration, and Infared and Raman spectra calculations allow complete characterization of the electronic and vibrational properties for the global minimum structural clusters.     

DFT Studies on the Stoichiometric Thorium Oxide Clusters(ThO_2)_n(n = 1～5): Electronic and Structural Properties

Density functional theory(DFT) calculations are performed to investigate the electronic and structural properties of the stoichiometric thorium oxide clusters(ThO_2)_n-/0(n = 1～5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies(VDEs)which are used to simulate the anionic photoelectron spectra(PES). Molecular orbital analyses are performed as well to analyze the chemical bonding in these thorium oxide clusters. The results show that the ground states of(ThO_2)_n-/0(n = 1～5) clusters prefer the low-spin structures. With increasing of the cluster size(n), the structure parameters of(ThO_2)_n-/0(n = 1～5) gradually evolve toward bulk thorium oxide species. It shows that both the coordination number and the average bond length increase gradually in(ThO_2)_n-/0(n = 1～5) to approach that of ThO2 bulk. What's more, the vibration frequencies of Th=O double bonds are found to be decreasing along with the increased cluster size.     

Theoretical Investigation on the Interaction of C2H Radical with Small Gold Clusters Au n 0/− (n = 1–4)

A density-functional theory investigation on the interactions between C₂H radical and small gold clusters Au _n ^0/? (n = 1–4) has been performed. The calculated results predict that C₂H radical inclines to interact with small gold clusters Au _n ^0/? (n = 1–4) as an integrity in the most stable structures of C₂HAu _n ^0/? (n = 1–4). The Au _n ^0/? (n = 1–4) clusters retain their structural integrity as units in the ground states of C₂HAu _n ^0/? (n = 1–4). The stretching vibrational frequencies of C≡C and C–H in the ground states of C₂HAu _n ^? (n = 1–4) are decreased compared with those of the C₂H radical due to the interaction between the Au _n ^0/? clusters and C₂H radical. Smaller red shifts in the C≡C and C–H stretching bands of C₂HAu _n ^? occur with an increase in n. The photoelectron spectra of the most stable structures of C₂HAu _n ^? (n = 1–4) have been simulated to aid their future experimental characterizations. The current study provides further insight into the interaction between C₂H radicals and gold clusters, which may lead to exploitation of the high activity of gold nanocrystals.