The chemical environment and structural ordering in liquid Mg-Y-Zn system:An ab-initio molecular dynamics investigation of melt for the formation mechanism of LPSO structure

In an effort to clarify the formation mechanism of LPSO structure in Mg-Y-Zn alloy,the chemical environment and structural ordering in liquid Mg-rich Mg-Y-Zn system are investigated with the aid of ab-initio molecular dynamics simulation.In liquid Mg-rich Mg-Y alloys,the strong Mg-Y interaction is determined,which promotes the formation of fivefold symmetric local structure.For Mg-Zn alloys,the weak Mg-Zn interaction results in the fivefold symmetry weakening in the liquid structure.Due to the coexistence of Y and Zn,the strong attractive interaction is introduced in liquid Mg-Y-Zn ternary alloy,and contributes to the clustering of Mg,Y,Zn launched from Zn.What is more,the distribution of local structures becomes closer to that in pure Mg compared with that in binary Mg-Y and Mg-Zn alloys.These results should relate to the origins of the Y/Zn segregation zone and close-packed stacking mode in LPSO structure,which provides a new insight into the formation mechanism of LPSO structure at atomic level.

Ab-initio and DFT Calculations of PdCl_2L_2 (L = DHSO, DPSO) Complexes

The substituent effect of sulfoxides in solvent extraction of palladium is investigated theoretically by using di-n-hexyl and diphenyl sulfoxide-palladium （Ⅱ） adducts as model complexes. RHF, DFT and two half-and-half functional （BHandHLYP and BHandH） methods have been applied in the geometry optimization, and BHandH method at the 6-31G^＊ level （Pd, 3-21G^＊） can give adequate accuracy for both free sulfoxides and their Pd （Ⅱ） complexes. As compared to diphenyl sulfoxide （DPSO）, the better affinity of di-n-hexyl sulfoxide （DHSO） towards Pd（Ⅱ） has been reasonably explained by a stronger electronic transfer, shorter Pd-S bond length and a larger binding energy in its Pd （Ⅱ） complex.

Atomic relaxation,stability and electronic properties of Mg2Sn(100)surfaces from ab-initio calculations

Mg2Sn(100)surfaces were investigated using ab-initio method based on density functional theory in order to explore the surface properties.It is found that both the eleven-layers for Mg-termination surfaces and the nine-layers for Sn-termination surfaces are all converged very well.The effects of relaxation mainly occurred within the three outermost atomic layers for both Mg and Sn terminations during the surface relaxation.Mg-termination surfaces are more stable than Sn-termination surfaces according to the analysis of surface energy.The density of states reveals the metallic property of both Mg-termination and Sn-termination surfaces.Covalent bonding exists in Mg2Sn(100)surfaces according to the analysis of partial density of states.

H_2-H_2各向异性作用势的ab-initio法计算

选用aug-cc-pVTZ及aug-cc-pVQZ基组对不同H2-H2位形进行了量子化学计算,外推出了氢分子间各向异性ab-initio作用势。依据实验数据确定出氢分子相互作用的5-体模型,在全局最优算法基础上拟合出了包含电四极矩项、多体极化作用项及三体关联项等在内的氢分子间各向异性作用势。结果验证了拟合势与ab-initio势能曲线几乎重合,两者偏差落在(-1.35K,1.29K)范围内;得出的氢分子第二维里系数与实验结果一致。

Magnetic properties of Mn-doped GaN with defects:ab-initio calculations

According to first-principles density functional calculations, we have investigated the magnetic properties of Mn- doped GaN with defects, Ga1-x-yVGxMny N1-z-tVNzOt with Mn substituted at Ga sites, nitrogen vacancies VN, gallium vacancies VG and oxygen substituted at nitrogen sites. The magnetic interaction in Mn-doped GaN favours the ferromagnetic coupling via the double exchange mechanism. The ground state is found to be well described by a model based on a Mn3＋-d5 in a high spin state coupled via a double exchange to a partially delocalized hole accommodated in the 2p states of neighbouring nitrogen ions. The effect of defects on ferromagnetic coupling is investigated. It is found that in the presence of donor defects, such as oxygen substituted at nitrogen sites, nitrogen vacancy antiferromagnetic interactions appear, while in the case of Ga vacancies, the interactions remain ferromagnetic; in the case of acceptor defects like Mg and Zn codoping, ferromagnetism is stabilized. The formation energies of these defects are computed. Furthermore, the half-metallic behaviours appear in some studied compounds.

<i>Ab-Initio</i>Computations of Electronic, Transport, and Structural Properties of <i>zinc-blende</i>Beryllium Selenide (<i>zb</i>-BeSe)

We report results from several ab-initio computations of electronic, transport and bulk properties of zinc-blende beryllium selenide (zb-BeSe). Our nonrelativistic calculations utilized a local density approximation (LDA) potential and the linear combination of atomic orbitals (LCAO). The key distinction of our calculations from other DFT calculations is the implementation of the Bagayoko, Zhao and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF), in the LCAO formalism. Our calculated, indirect band gap is 5.46 eV, from &Gamma;to a conduction band minimum between Г and X, for a room temperature lattice constant of 5.152 &Aring;. Available, room temperature experimental band gaps of 5.5 (direct) and 4 - 4.5 (unspecified) point to the need for additional measurements of this gap. Our calculated bulk modulus of 92.35 GPa is in excellent agreement with experiment (92.2 &plusmn;?1.8 GPa). Our predicted equilibrium lattice constant and band gap, at zero temperature, are 5.0438 &Aring;and 5.4 eV, respectively.

Modern Ab-Initio Calculations on Modified Tomas-Fermi-Dirac Theory

Thomas-Fermi theory is an approximate method, which is widely used to describe the properties of matter at various hierarchical levels (atomic nucleus, atom, molecule, solid, etc.). Special development is achieved using Thomas-Fermi theory to the theory of extreme states of matter appearing under high pressures, high temperatures or strong external fields. Relevant sections of physics and related sciences (astrophysics, quantum chemistry, a number of applied sciences) determine the scope of Thomas-Fermi theory. Popularity Thomas-Fermi theory is related to its relative simplicity, clarity and versatility. The latter means that the result of the calculation by Thomas-Fermi theory applies immediately to all chemical elements: the transition from element to element is as simple scale transformation. These features make it to be a highly convenient tool for qualitative and, in many cases, and quantitative analysis.

Physical Properties of the Zn_xCd_1-xSe Alloys: Ab-Initio Method

The present work performs self-consistent ab initio full-potential linear muffin-tin orbital (FP-LMTO) method to study the structural and electronic properties of the ternary ZnxCd1-xSe alloy, based on density functional theory (DFT). In this approach, both the local density approximation (LDA) and the generalized gradient approximation (GGA) were used for the exchange-correlation potential calculation. The ground-state properties are determined for the bulk materials CdSe, ZnSe and their alloy in cubic phase. In particular, the lattice constant, bulk modulus, electronic band structures and effective mass. We mainly showed deviation of the lattice parameter and bulk modulus from Vegard’s law of our alloys. We also presented the microscopic origins of the gap bowing using the approach of Zunger et al. The results are compared with other theoretical calculations and experimental data and are in reasonable agreement.

A Study by Ab-Initio Calculation of Structural and Electronic Properties of Semiconductor Nanostructures Based on ZnSe

Our calculations are based on the modeling technique and simulation Ab-Initio that appeals to the Density Functional Theory (DFT) relying on the Full-Potential Linearized Augmented Plane Waves (FP-LAPW) method that requires a calculation process using approximations such as Local Density (LDA) and Generalized Gradient (GGA) developed in the modelling software of nanostructures WIEN2k. The optimal structure of the binary semiconductor ZnSe crystallizing in the complex phase of Zinc Blende (B3) was determined by studying the variation of energy depending on the volume of the elementary cell. Then the electronic properties of the optimized state were analyzed such as the gap energy, the total density of states (TDOS), the partial density of states (PDOS) and the repartition of the electronic charge density. The obtained results were successful compared with other theoretical and experimental values reported in literature.

An ab-initio study of a^1B_(3u)→X^1A_g transition in a neutral molecular N_2 dimer

Presents the ab initio calculations performed for different symmetry groups of neutral molecular N 2 dimer, and the calculation of ground state and low lying singlet excited states for each symmetry group and concludes from the results that there is an electric dipole transition between X 1A g and a 1B 3u (singlet singlet) excited states belonging to D 2h group symmetry, and discusses the vibrational energy levels and emission spectra calculates for this transition.

<i>Ab-Initio</i>Calculations of 27 Electronic States of the BP⁺Ion-Molecule

The theoretical investigation of the potential energy curves, in the representation 2s+1Λ(+/-), of the 27 low-lying Doublet and Quartet electronic states of the BP+ molecular ion has been performed with the methods in quantum chemistry, the Complete Active Space Self Consistent Field (CASSCF) and the Multireference Configuration Interaction (MRCI) calculations. The harmonic vibrational frequency ωe, the inter-nuclear distance at equilibrium Re, the rotational constant Be, the electronic energy with respect to the minimum ground state energy Te, and the permanent dipole moment have also been calculated. Twenty-three new electronic states have been investigated here for the first time. The comparison between the values of the present work and those available in the literature for several electronic states shows a good agreement. These investigated data can be a conducive to further work on BP+ molecular ion in both experimental and theoretical research.

ZnO(110)衬底上单层黑磷烯的外延生长

二维黑磷烯作为新一代半导体材料,具有可调带隙和高载流子迁移率等优点,具有广阔的应用前景.但二维黑磷烯目前还不能直接大规模制备,限制了其进一步的研究和应用.分子束外延是一种广泛使用的具有较高外延质量的单晶薄膜生长方法,在制备二维黑磷烯方面具有广阔的应用前景.本文基于密度泛函理论计算筛选了ZnO(110)、GaN(110)、BP(110)和SiC(110)四种潜在的衬底,研究了二维黑磷烯在这些衬底上的生长情况.研究表明,ZnO(110)上的黑磷单层及团簇结构是稳定的,且磷在该表面扩散特性也有助于磷团簇的成核生长.本研究为高效制备二维黑磷烯及其他二维材料提供了有益的指导.

Conductivity of carbon-based molecular junctions from ab-initio methods

Carbon nanomaterials （CNMs） are prompting candidates tor next generational electronics. In this review we provide a mini overview of recent results on the conductivity of carbon-based molecular junctions obtained from ab-mitio methods. CNMs used as nanoelectrodes and molecular materials in molecular junctions are discussed. The flmctionalities that include the nanomechanically controlled molecular conductance switches, negative differential resistance devices, and electronic rectifiers realized by using CNMs have been demonstrated.

Quantitative structure-property relationship study of cathode volume changes in lithium ion batteries using ab-initio and partial least squares analysis

In this paper,we report a method through the combination of ab-initio calculations and partial least squares(PLS)analysis to develop the Quantitative Structure eActivity Relationship(QSAR)formulations of cathode volume changes in lithium ion batteries.The PLS analysis is based on ab-initio calculation data of 14 oxide cathodes with spinel structure LiX2O4 and 14 oxide cathodes with layered-structure LiXO_(2)(X=Ti,V,Cr,Mn,Fe,Co,Ni,Nb,Mo,Ru,Rh,Pd,Ta,Ir).Five types of descriptors,describing the characteristics of each compound from crystal structure,element,composition,local distortion and electronic level,with 34 factors in total,are adopted to obtain the QSAR formulation.According to the variable importance in projection analysis,the radius of X4t ion,and the X octahedron descriptors make major contributions to the volume change of cathode during delithiation.The analysis is hopefully applied to the virtual screening and combinatorial design of low-strain cathode materials for lithium ion batteries.

Strongly correlated intermetallic rare-earth monoaurides(Ln-Au):Ab-initio study

In this paper, we explored the structural, elastic and mechanical properties of the strongly correlated electron systems, intermetallic Ln-Au（Ln = Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu） in cubic structure,using PF-LAPW method within the density functional theory. Structural properties of these intermetallics were investigated by treating the exchange-correlation potential with the GGA-PBE, GGA-PBEsol and GGA ＋ U. The effectiveness of the U for the structural properties as compared to other methods confirms the strong correlated nature of these compounds and the calculated lattice constants endorse the divalency of Yb. The results demonstrate the stable cubic CsCl structure of these compounds. Bulk modulus, Young＇s modulus, shear modulus, B/G ratio, Cauchy pressure, Poisson＇s ratio, anisotropic ratio,Kleinman parameters and Lame＇s coefficients were studied using the PBEsol to evaluate their importance in various types of engineering applications. The most prominent features of these compounds are their ductility, very high melting points, resistance to corrosion, and anisotropic nature.

Strain effect on the electronic properties of III-nitride nanosheets:Ab-initio study

In this study the structural and electronic properties of III-nitride monolayers XN(X=B, Al, Ga and In) under different percentages of homogeneous and shear strain are investigated using the full potential linearized augmented plane wave within the density functional theory. Geometry optimizations indicate that GaN and InN monolayers get buckled under compressive strain.Our calculations show that the free-strains of these four monolayers have an indirect band gap. By applying compressive biaxial strain, a transition from indirect to direct band gap occurs for GaN and InN, while the character of band gap for BN and AlN is not changed. Under tensile strain, only BN monolayer behaves as direct band gap semiconductor. In addition, when the shear strain is applied, only InN undergoes an indirect to direct band gap transition. Furthermore, the variations of band gap versus strain for III-nitride monolayers have been calculated. When a homogeneous uniform strain, in the range of [.10%, +10%], is applied to the monolayers, the band gap can be tuned for from 3.92 eV to 4.58 eV for BN, from 1.67 eV to 3.46 eV for AlN, from0.24 eV to 2.79 eV for GaN and from 0.60 eV to 0.90 eV for InN.

两个丁二肟有机锡配合物的合成、结构及抗癌活性

合成了2个丁二酮肟有机锡化合物:双(三(2-甲基-2-苯基丙基)锡)丁二酮肟配合物(C_(6)H_(5)C(CH_(3))_(2)CH_(2))_(3)Sn(ON=C(CH_(3))C(CH_(3))=NO)Sn(CH_(2)C(CH_(3))_(2)C_(6)H_(5))_(3)(1)和二苄基锡氧氯丁二酮肟多核配合物[μ_(3)-O-((C_(6)H_(5)CH_(2))_(2)Sn)_(2)(ON=C(CH_(3))C(CH_(3))=NOH)(O)Cl]_(2)(2)。通过元素分析、红外光谱、核磁共振(^(1)H、^(13)C、^(119)Sn)、差热分析和单晶X射线衍射对配合物进行了结构表征,对其结构进行量子化学从头计算,并进行了体外抗癌活性研究。结果显示:配合物1为通过配体丁二酮肟桥联的双锡核中心对称分子,锡原子均为四配位的畸变四面体构型;配合物2为通过氧原子和丁二酮肟配体桥联的四锡核中心对称多环聚合结构,锡原子分别为五配位的畸变三角双锥构型和六配位的畸变八面体构型。配合物对人肝癌细胞(HUH7)、人肺癌细胞(A549)、人表皮癌细胞(A431)、人结肠癌细胞(HCT-116)和人乳腺癌细胞(MDA-MB-231)均有较强的抑制活性。

温稠密物质模拟的第一性原理方法进展

温稠密物质(Warm Dense Matter,WDM)是介于凝聚态物质和等离子体之间的一种过渡状态的物质,也是行星物理、实验室天体物理和惯性约束聚变等高能量密度物理领域的前沿科研方向。温稠密物质的量子效应显著,具有部分电离、强耦合、电子简并和热效应等重要的物理性质,因此需要采用量子力学的基础理论来描述。近年来,基于量子力学的第一性原理计算模拟方法发展迅速,逐渐成为了深入理解温稠密物质性质的有效工具。一方面,直接将凝聚态物理和材料科学中广泛适用的第一性原理方法应用于温稠密物质面临着巨大的挑战,特别是在宽温区和极端高压等极端条件下,需要不断改进现有的第一性原理算法和软件。另一方面,基于机器学习的分子动力学方法发展迅速,也给温稠密物质模拟带来了新的工具。在这篇综述中,我们首先回顾了适用于温稠密物质模拟的传统第一性原理方法,包括Kohn-Sham密度泛函理论方法和无轨道密度泛函理论方法。其次,我们介绍了近年来发展的新方法和软件,例如改进的第一性原理方法和随机密度泛函理论方法,后者已在国产开源密度泛函理论软件原子算筹(ABACUS)中实现。以上新方法可以显著提升温稠密物质的计算规模和效率,从而提升温稠密物质的结构、动力学和输运系数等性质的计算精度。

Maxwell Equations and Magnetic Monopoles

The manuscript introduces an “ab initio” quantum model to deduce the Maxwell equations. After general considerations and laying out the model’s theoretical framework, these equations can be derived alongside a broad variety of other results. Specifically, a corollary of the present model proposes a possible mechanism underlying the formation of magnetic monopoles and allows estimating their formation energy in order of magnitude.