Density functional investigations for geometric and electronic properties of In4M and In12M （M = C,Si, In） clusters

First-principle calculations are performed to study geometric and electronic properties of both neutral and anionic In4M and In12M （M = C, Si, In） clusters. In4C and In4Si are found to be tetrahedral molecules. The icosahedral structure is found to be unfavourable for In12M. The most stable structure for In12C is a distorted buckled biplanar structure while for In12Si it is of an In-cage with the Si located in the centre. Charge effect on the structure of In12M is discussed. In4C has a significantly large binding energy and an energy gap between the highest-occupied molecularorbital level and the lowest unoccupied molecular-orbital level, a low electron affinity, and a high ionization potential, which are the characters of a magic cluster, enriching the family of doped-group-IIIA metal clusters for cluster-assembled materials.     

Density functional calculations on 13-atom Pd12M （M= Sc-Ni） bimetallic clusters

The geometric structures,electronic and magnetic properties of the 3d transition metal doped clusters Pd12M(M=Sc-Ni) are studied using the semi-core pseudopots density functional theory.The groundstate geometric structure of the Pd12M cluster is probably of pseudoicosahedron.The Ih-Pd12M cluster has the most thermodynamic stability in five different symmetric isomers.The energy gap shows that Pd12M cluster is partly metallic.Both the absolutely predominant metal bond and very weak covalent bond might exist in the Pd12M cluster.The magnetic moment of Pd12M varies from 0 to 5 μB,implying that it has a potential application in new nanomaterials with tunable magnetic properties.     

Ab initio investigations of the charge transport properties of endohedral M@C20（M=Na and K）metallofullerenes

Using density functional theory and quantum transport calculations based on nonequilibum Green’s function formalism,we investigate the charge transport properties of endohedral M@C 20 (M=Na and K) metallofullerenes.Our results show that the conductance of C 20 fullerene can be obviously improved by insertion of alkali atom at its centre.Both linear and nonlinear sections are found on the I-V curves of the Au-M@C 20-Au two-probe systems.The novel negative differential resistance behaviour is also observed in Na@C 20 molecule but not in K@C 20.     

The Formation Mechanism and Binding Energy for the Octahedral Central Structure of the He7^＋ Cluster

The formation mechanism for the octahedral central structure of the He7^ cluster is proposed and its total energy curve is calculated by the method of a modified arrangement channel quantum mechanics (MACQM). The energy is a function of separation R between two nuclei at the center and an apex of the octahedral central structure. The result of the calculation shows that the curve has a minimM energy -19.7296 a.u. at R = 2.40α0. The binding energy of He7^ with respect to He^ 6He was calculated to be 0.6437 a.u. This means that the duster of He7^ may be formed in the stable octahedral central structure with R=2.40 α0.     

First-principles study of the （001） surface of cubic PbHfO3 and BaHfO3

Using first-principles techniques,we investigate the(001) surfaces of cubic PbHfO3(PHO) and BaHfO3(BHO) terminated with both AO(A=Pb and Ba) and HfO2.Surface structure,partial density of states,band structure,and surface energy are obtained.The BaO surface is found to be similar to its counterpart in BHO.For the HfO2-terminated surface of cubic PHO,the largest relaxation appears on the second-layer atoms but not on the first-layer ones.The analysis of the structure relaxation parameters reveals that the rumpling of the(001) surface for PHO is stronger than that for BHO.The surface thermodynamic stability is explored,and it is found that both the PbO-and the BaO-terminated surfaces are more stable than the HfO2-terminated surfaces for PHO and BHO,respectively.The surface energy calculations show that the(001) surface of PHO is more easily constructed than that of BHO.     

High stability of the goldalloy fullerenes:A density functional theory investigation of M₁₂@Au₂₀（M=Na,Al,Ag,Sc,Y,La,Lu,and Au） clusters

Discovering highly stable metal fullerenes such as the celebrated C 60 is interesting in cluster science as they have potential applications as building blocks in new nanostructures.We here investigated the structural and electronic properties of the fullerenes M 12 @Au 20(M=Na,Al,Ag,Sc,Y,La,Lu,and Au),using a first-principles investigation with the density functional theory.It is found that these compound clusters possess a similar cage structure to the icosahedral Au 32 fullerene.La 12 @Au 20 is found to be particularly stable among these clusters.The binding energy of La 12 @Au 20 is 3.43 eV per atom,1.05 eV larger than that in Au 32.The highest occupied molecular orbital-lowest unoccupied molecular orbital(HOMO-LUMO) gap of La 12 @Au 20 is only 0.31 eV,suggesting that it should be relatively chemically reactive.     

Formation Mechanism and Binding Energy for Icosahedral Central Structure of He13^＋ Cluster

The formation mechanism for the icosahedral central structure of the He13^ cluster is proposed and its total energy curve is calculated by the method of a Modified Arrangement Channel Quantum Mechanics. The energy is the function of separation R between two nuclei at the center and an apex of the icosahedral central structure. The result of the calculation has shown that the curve has a minimal energy -37.5765 (a.u.) at R=2.70ao. The binding energy of He13^ with respect to He^ 12He was calculated to be 1.4046 a.u. This means that the cluster of He13^ may be formed in an icosahedral central structure with strong binding energy.     

Phase transition and thermodynamic properties of ThO2：Quasi-harmonic approximation calculations and anharmonic effects

The thermodynamic properties and the phase transition of ThO2 from the cubic structure to the orthorhombic structure are investigated using the first-principles projector-augmented wave method. The vibrational contribution to Helmholtz free energy is evaluated from the first-principles phonon calculations. The anharmonic contribution to quasi-harmonic free energy is accounted for by using an effective method(2010 Phys. Rev. B 81 172301). The results reveal that at ambient temperature, the phase transition from the cubic phase to the orthorhombic phase occurs at 26.45 GPa, which is consistent with the experimental and theoretical data. With increasing temperature, the transition pressure decreases almost linearly. By comparing the experimental results with the calculation results, it is shown that the thermodynamic properties of ThO2 at high temperature improve substantially after including the anharmonic correction to quasi-harmonic free energy.     

High stability of the goldalloy fullerenes：A density functional theory investigation of M_（12）@Au_（20）（M=Na,Al,Ag,Sc,Y,La,Lu,and Au） clusters

Discovering highly stable metal fullerenes such as the celebrated C 60 is interesting in cluster science as they have potential applications as building blocks in new nanostructures.We here investigated the structural and electronic properties of the fullerenes M 12 @Au 20（M=Na,Al,Ag,Sc,Y,La,Lu,and Au）,using a first-principles investigation with the density functional theory.It is found that these compound clusters possess a similar cage structure to the icosahedral Au 32 fullerene.La 12 @Au 20 is found to be particularly stable among these clusters.The binding energy of La 12 @Au 20 is 3.43 eV per atom,1.05 eV larger than that in Au 32.The highest occupied molecular orbital-lowest unoccupied molecular orbital（HOMO-LUMO） gap of La 12 @Au 20 is only 0.31 eV,suggesting that it should be relatively chemically reactive.     

A close look at the competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei

competition of isovector and isoscalar pairing in A=18 and 20 even-even N≈Z nuclei is analyzed in the framework of the mean-field plus the dynamic quadurpole-quadurpole, pairing and particle-hole interactions, whose Hamiltonian is diagonalized in the basis U(24) ?(U(6) ? S U(3) ? S O(3))■(U(4) ? S US(2)■ S UT(2)) in the L = 0 configuration subspace. Besides the pairing interaction, it is observed that the quadurpole-quadurpole and particlehole interactions also play a significant role in determining the relative positions of low-lying excited 0~+ and 1~+ levels and their energy gaps, which can result in the ground state first-order quantum phase transition from J = 0 to J = 1.The strengths of the isovector and isoscalar pairing interactions in these even-even nuclei are estimated with respect to the energy gap and the total contribution to the binding energy. Most importantly, it is shown that although the mechanism of the particle-hole contribution to the binding energy is different, it is indirectly related to the Wigner term in the binding energy.     

The stability, frontier orbitals, bond character, and static linear polarizability of the fluorinated fullerene H20@C80F60

This paper uses the density functional theory under generalised gradient approximation to analyse the stability,frontier orbitals,bond character,and static linear polarizability of H20@C80F60,which has not been isolated,as well as those of the synthesised H 20 @C 80 H 60.The H20@C80F60 should be considerably stable by analysing its energy and aromaticity.The inside H and outside X will play different role in the chemical reaction involving H 20 @C 80 X 60(X=H and F).The covalence of C-H bond is in the order that the inside C-H bond of H20@C80F60 > the inside C-H bond of H 20 @C 80 H 60 > the outside C-H bond of H 20 @C 80 H 60,whereas the C-F bond of H20@C80F60 have both the covalent and ionic characters.The static linear polarizabilities of C 80 and H 20 @C 80 X 60(X=H and F) are all isotropic.     

MC20F20（M=Li，Na，Be和Mg）几何结构和电子性质的密度泛函计算研究

采用密度泛函理论（density functional theory, DFT）中的广义梯度近似（generalized gradient approximation, GGA）对MC₂₀F₂₀（M=Li,Na,Be和Mg）的几何结构和电子性质进行了计算研究.几何结构研发现：随着内掺原子序数的增加,金属原子M对C₂₀F₂₀中的C—C键的影响越来越大,而对C—F键的影响甚微.掺杂能计算表明：MC₂₀F₂₀的掺杂能均为负值,需要在一定的实验条件下才能被合成.内掺碱金属和碱土金属分别产生了两类截然不同的能隙和磁性.其中,内掺碱金属的能隙非常小,且带有1μ_B的净磁矩,表现出磁性;而内掺碱土金属的能隙比C₆₀的能隙还大,净自旋为0,表现出非磁性. 关键词： 富勒烯 几何结构 电子结构 密度泛函     

内掺过渡金属富勒烯衍生物Ni@C20H20几何结构、成键和电磁性质的密度泛函计算研究

采用密度泛函理论中的广义梯度近似对Ni@C₂₀H₂₀的几何结构、成键和电磁性质进行密度泛函计算研究.结构优化发现位于偏离笼子中心三种位置处的Ni原子优化之后均回到笼子中心.结合能和能隙分析表明C₂₀H₂₀的中心位置是Ni原子热力学和动力学最稳定的位置.成键分析表明：Ni原子位于C₂₀H₂₀中心时,和C原子之间几乎没有相互作用,保持自己的孤立状态.电磁分析表明：原子磁矩为2关键词： 20H₂₀')" href="#">C₂₀H₂₀ 20H₂₀')" href="#">Ni@C₂₀H₂₀ 几何结构 成键 电磁性质 密度泛函理论     

C72,La2@C72几何结构和电子性质的计算研究

采用密度泛涵理论(density functional theory, DFT)中的广义梯度近似(generally gradient approximation, GGA)对富勒烯C₇₂和内掺金属La富勒烯La₂@C₇₂三种同分异构体的几何结构和电子结构进行研究.发现在C₇₂的三种同分异构体中，满足独立五边形规则(isolated-pentagon-rule，IPR)的C₇₂(D_{6d< 关键词： 72}')" href="#">C₇₂ 2@C₇₂')" href="#">La₂@C₇₂ 密度泛涵理论 几何结构 电子结构     

内掺过渡金属非典型富勒烯M@C22(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni) 几何结构、电子结构、稳定性和磁性的密度泛函研究

采用密度泛函理论中广义梯度近似对非典型富勒烯C₂₂和过渡金属内掺衍生物M@C₂₂(M=Sc,Ti,V,Cr,Mn,Fe,Co和Ni)的几何结构和电子结构进行计算研究.发现非典型富勒烯C₂₂的基态结构是含有一个四碳环的单重态笼状结构.过渡金属原子的掺入明显提高了体系的稳定性. C-M键既有一定共价性又有一定离子性.磁性、能级图、轨道分布和态密度图分析表明: M原子的3d轨道和碳笼的C原子的原子轨道之间存在较强的轨道杂化. Ti, Cr, Fe和Ni内掺的结构出现磁性完全猝灭现象. Sc和碳笼间是弱反铁磁作用, V,Mn和Co与碳笼间是弱铁磁作用.     

The density functional study of the stabilities,bond characters,static linear polarisabilities,and aromaticities of the ’in-out’ isomerism Hn-60@CnH60（n=70,72,74）

This paper uses the density functional theory to analyse the stabilities,bond characters,static linear polarisabilities,and aromaticities of the ’in-out’ isomerism H n-60 @C n H 60 (n=70,72,74).The binding energies,C-H bond energies,and energy gaps explore that the ’in-out’ isometric perhydrogenation of C n (n=70,72,74) can remarkably improve the stabilities.The static linear polarisabilies of H n-60 @C n H 60 (n=70,72,74) are indeed relative to their shapes,while they show almost nonaromatic character.This study can suggest that the ’in-out’ isometric perhydrogenation of fullerenes could lead to the invention of entirely novel potential hydrogen storage nanomaterials.     

过渡族金属替代元素M对YFe11M系统的磁性质的影响

基于密度泛函理论(DFT),采用线性缀加平面波展式结合改进的局域轨道方法(APW+lo),对具有ThMn₁₂结构的永磁材料YFe₁₁M(M=Sc,V等)的结构和磁性进行了计算和分析.探讨了过渡族金属替代元素M在YFe₁₁M中系统的最佳可能占位.讨论了不同替代元素M对YFe₁₁M系统的磁性质的影响. 关键词： 11M')" href="#">YFe₁₁M 密度泛函 晶体结构 磁矩     

ANISOTROPY OF OPTICAL ABSORPTION INTENSITY IN Tm3+ DOPED YVO4 CRYSTALS

Seven absorption group-bands (¹D₂, ¹G₄, ³F₂, ³F₃, ³H₄, ³H₅, ³F₄) of Tm³⁺ in YVO₄ single crystals have been observed in the orientation absorption spectra recorded in the spectral range from 200 to 4000 nm at 300K. The integrated absorption cross section for each group-band was accurately evaluated. On the assumption that the anisotropy of this uni-axial crystal is small, the Judd-Ofelt theory was extended for the calculation of 4f-4f transition intensities of Tm³⁺ in YVO₄. Two sets of phenomenological intensity parameters were derived from a least-squares-fit procedure. For c-axis cut sample we have Ω₂=10.18 (10^-20cm²), Ω₄=1.96 (10^-20cm²), Ω₆=0.75 (10^-20cm²).For a-axis cut sample we have Ω₂=8.20 (10^-20cm²), Ω₄=2.47 (10^-20cm²), Ω₆=0.91 (10^-20cm²). The anisotropy of the optical absorption intensities of Tm³⁺:YVO₄ was theoretically analyzed in detail.     

插层化合物LixTiS2中Li离子-空位二维有序结构稳定性的第一性原理研究

根据局域密度近似下的密度泛函理论，用第一性原理方法对TiS₂，LiTiS₂和Li_xTiS₂(x=1/4, 1/3, 1/2, 2/3, 3/4)有序系统进行了几何优化和总能量计算.将计算结果与已有的实验和理论结果进行了对比，得到的归一化结构参量增量Δa₀和Δc₀随离子浓度单调地增加，与实验结果符合较好.Li_{关键词： x}TiS₂')" href="#">Li_xTiS₂ 有序结构 第一性原理计算 密度泛函理论