Some solvable models of nonuniform classical fluids

A model classical fluid is constructed by assuming that the direct correlation functionc(r – r) is independent of any applied external field. Thermodynamic consistency requires thatc(r – r) 0, and permits explicit representation of the model by a many-body interaction potential. In the canonical ensemble, the model shows a phase transition to an infinite density condensed phase, but in the grand canonical ensemble only an anomalous transition to zero density vapor is found to stably exist.     

甘氨酸和丙氨酸二肽、三肽中N-H…O=C分子内氢键键能的理论研究

提出一种计算多肽中N-H…O=C分子内氢键键能的新方法.并将新方法应用于计算甘氨酸和丙氨酸二肽、三肽中N-H…O=C分子内氢键键能.利用密度泛函理论B3LYP/6-31G(d)方法优化几何构型和计算频率.对全部结构计算MP2/6-311 G(3df,2p)水平上的单点能量.结果表明:在甘氨酸二肽中氢键键能为-6.38 kcal/mol,在丙氨酸二肽中氢键键能为-7.09-、6.25 kcal/mol;在甘氨酸三肽中氢键键能为-5.62 kcal/mol,在丙氨酸三肽中氢键键能为-5.37,-5.74 kcal/mol.     

烃类化合物碳氢键解离焓的密度泛函理论研究

通过比较10种密度泛函方法对烃类化合物碳氢键解离焓的计算精度, 发现新型密度泛函BMK方法具有最高的计算精度. 利用该方法计算了包含饱和链烃,、不饱和链烃、脂环烃和芳香烃在内的172个烃类化合物的碳氢键解离焓,计算均方根误差仅为7.95 kJ•mol^－1, 线性拟合常数为0.985. 通过自然键轨道法分析发现, 烃类物质的碳氢键解离焓与母体的碳氢键杂化轨道成分p%, 自由基奇电子轨道杂化成分p%及自由基的自旋密度三个参数之间存在较好的定量关系. 此外, 饱和链烷烃及不饱和链烃的碳氢键解离焓与碳氢键键长之间也存在较好的线性关系.     

四角晶相HfO2(001)表面原子和电子结构研究

采用基于第一性原理的密度泛函理论研究了四角晶相二氧化铪(t-HfO₂)体相及 其(001)表面的原子几何与电子结构.理论计算结果表明，t-HfO₂(001)表面不会 产生重构现象.与体相电子结构相比, t-HfO₂(001)表面态密度明显高于体相态 密度.其次，表面原子的态密度更靠近费米能级(E_F)，价带往低能量处移动，并 有表面态产生.计算结果表明了t-HfO₂表面禁带宽度明显低于体相的禁带宽度. t-HfO₂(001)的表面态产生以及表面禁带宽度减小是由于Hf原子与O原子的配位 数减少，表面原子周围的环境发生变化而引起的. 关键词： 密度泛函理论 2(001)')" href="#">t-HfO₂(001) 表面电子结构     

Piezoelectricity of ordered (ScxGa1-xN) alloys from first principles

First-principles calculations are performed to compute the e₃₃ piezoelectric coefficients of GaN, ScN and (Sc_xGa_1-xN) alloys exhibiting an alternation of hexagonal GaN, with hexagonal ScN along the c-axis. For Sc compositions larger than 50%, each atom has nearly five nearest neighbors (i.e., the ground state exhibits a phase that is five-fold coordinated). On the other hand, Sc-deficient (Sc, Ga) N alloys adopt a ground-state that is four-fold coordinated). The magnitude of e₃₃ in the Sc-deficient ideally ordered (Sc_0.25Ga_0.75N) is found to be larger than the magnitude of the corresponding e₃₃ coefficients resulting from the compositional weighted average over the hexagonal (h-ScN) and the wurtzite (w-GaN) parent compounds. On the other hand, the e₃₃ coefficients of the Sc-rich ordered (Sc_0.75Ga_0.25N) is found to be negligibly small. In addition, e₃₃ piezoelectric coefficients in ordered (Sc_0.5Ga_0.5N) exhibit quite large magnitudes, due to the nonpolar to polar transition occurs at Sc composition x = 0.5, and thus can bridge the corresponding coefficients of (Ga, In) N and ferroelectric alloys. The microscopic origins for this huge enhancement in the piezoelectric behavior in Sc-low and Sc-intermediate alloys and the role of each atom are revealed and discussed.     

协变密度泛函理论中的张量力效应

张量力是核子-核子相互作用的重要成分,被认为是理解奇特原子核中壳结构演化规律的关键要素。然而,目前对于核介质中的张量力及其效应的定量认识,仍存在很多亟待解决的关键问题。着重梳理了在原子核密度泛函理论框架下,研究有效相互作用中的张量力成分以及相应的张量力效应的相关工作,重点包括:基于相对论Hartree-Fock理论,以同位素链中的质子幻数壳演化为例,定量提取与分析其中的张量力效应;以及基于第一性原理的相对论Brueckner-Hartree-Fock理论,以中子滴单粒子能谱中的自旋-轨道劈裂演化为例,提出与张量力效应相关联的"准实验数据"。最后,展望原子核密度泛函理论今后可能的发展策略。Tensor force is one of the most important components of the nucleon-nucleon interaction. It plays a critical role in understanding the shell evolution in exotic nuclei. However, there are still several puzzles concerning the tensor force and its effects in the nuclear medium. In this paper, we mainly focus on the studies of tensor force in the effective interactions and its effects in finite nuclear systems within the scheme of nuclear density functional theory. In particular, we highlight the recent developments, including the quantitative analysis of tensor effects in the relativistic Hartree-Fock theory by taking the evolution of proton magic shells in the isotopic chains as an example, and the "meta-data" of tensor effects provided by the ab initio relativistic Brueckner-Hartree-Fock theory by taking the evolution of spin-orbit splitting in the single-particle spectra of neutron drops as an example. Perspectives are focused on the possible strategies for the future developments of nuclear density functional theory.     

First-principles investigation of chemical modification on two-dimensional iron–phthalocyanine sheet

Successful synthesis of single iron–phthalocyanie(FePc) framework layer on substrate and its transferrable properties open the door for decorating the separately distributed transition metals for exploring the diverse properties. We have studied the effects of chemical modification on two-dimensional FePc organometallic framework with density functional theory. For simplicity, the non-metal atoms with variant valence electrons are used as prototypes to estimate the effects from chemical modifications with different functional groups. The thermo-stabilities of the non-metal atom decorated complex sheet materials have been estimated by the first-principles constant energy molecular dynamic simulations. Upon the nonmetal atom adsorption, the magnetic moment could be changed from 2 μBto 0, 1, 2, and 3 μBper unit cell for the case of tetra-, penta-, hexa-, and hepta-valent non-metal modifications, respectively, showing interesting promise to tailor its magnetic properties for potential applications.     

Adsorption dynamics of O2 on Cu(1 0 0)

We have studied the adsorption of O₂ on the Cu(1 0 0) surface using both static potential energy surface (PES) calculations and ab initio molecular dynamics. The dynamical calculations complement the PES results, revealing steering effects which could not be predicted based on the static calculations only. We study the effect of oxidation and Ag doping on O₂ adsorption dynamics. The results are discussed in the light of recent molecular beam experiments.     

New collective modes of interaction nature in inhomogeneous Ising networks

We propose a vertex formulation of the Ising model with inhomogeneous external field on multiconnected networks possessing a superbond structure. The related technique based on gauge degrees of freedom enables us to recognize new collective modes of interaction nature, which provide an exact solution of the inverse profile problem and an explicit form of a local free-energy functional on an extended magnetization-mode space. Application is made to a square strip.     

Investigation of the dissociative adsorption for cyclopropane on the copper surface by density functional theory and quantum chemical molecular dynamics method

The dissociative adsorption of cyclopropane on the copper surface was studied using quantum chemical molecular dynamics method with “Colors-Excite” code and density functional theory by Amsterdam Density Functional program (ADF2000). The excited state of cyclopropane was used as adsorbate to simulate the dissociated adsorption under an irradiation energy of ca. 10 eV. One of the C-C bonds in cyclopropane was broken and the two new bonds between cyclopropane and copper surface were formed. The electrons transferred from the copper atoms to cyclopropane with a value of about 0.2e. The shorter distances between the carbons and surface copper atoms showed the existence of strong interaction. Consistently, the results indicated metallacyclopentane was the most possible intermediate species in dissociative adsorption by ADF2000 and “Colors-Excite” method.