氢原子在金属表面的吸附理论

本文在相关基函数理论框架下,利用巨分子模型,建立了氢原子在简单金属表面的吸附理论模型。通过对吸附平衡位置参量的变分数值计算,我们得到了关于氢原子在金属Al(r_s=2.07),Mg(r_s=2.66),Li(r_s=3.28)和Na(r_s=3.99)表面上的吸附能,吸附体系的电子密度以及平衡位置。对于传统的密度泛函方法得到的结果,本文作了比较。 关键词：     

金属表面的相关波函数理论(Ⅱ)——实际计算

在文献[1]给出的理论框架的基础上,由具有Feenberg-Jastrow关联因子的相关波函数,计算了“jellium”模型下简单金属的表面能和电子密度分布。表面电子密度分布由求解Cha-kravarty-Woo方程而得到。由于库伦关联的长程性,在表面能和CW积分方程中都出现一系列的发散项,本文证明了所有发散项严格互相抵消。本文求得的表面能在整个实际金属的电子密度范围内(r_s=2—6)与实验值大致符合。 关键词：     

半导体反型层中的电子关联和多体波函数

本文运用CBF(correlation basis function)理论,由电子间的有效势V_eff(R)和电子气的集体振荡行为,给出准二维电子体系——半导体反型层中的电子的关联因子U(R),得到该体系的对关联函数、关联能和多体波函数。 关键词：     

三套闭路格林函数的变换关系

给出三套闭路格林函数之间的变换关系和若干运算规则,同时得到多点推迟和超前格林函数的一般定义。证明多点格林函数之间的一些代数关系,是闭路上相连格林函数生成泛函W[J₊,J_-]_(J+=J-=J)=0这一性质的后果。 关键词：     

PuNO分子结构与势能函数

本文运用密度泛函理论的B3LYP方法, 对钚原子应用LANL2DZ收缩价基函数, 氮、氧原子采用AUG-cc-pVTZ基函数, 分别对PuN, PuO, NO和PuNO体系进行了结构优化, 得到PuNO分子最稳构型为C_∞v (Pu-N-O), 电子态为⁶Σ^- (基态), 平衡核间距R_ON=0.12257 nm, R_NPu=0.22951 nm, 离解能D_e=8.10537 eV. 同时优化得到PuNO 分子存在两种亚稳态平衡构型分别为C_∞v (Pu-O-N), ⁶Σ^- (电子态)和C_s (O-Pu-N), A" (电子态), 以及分子体系相应的力学常数等. 拟合出PuN, PuO 和NO 分子的Murrell-Sorbie势能函数, 并使用多体项展式理论得到了PuNO分子的分析势能函数, 其等值势能图准确再现了PuNO分子最稳态构型及两个亚稳态构型的离解能和结构特性, 由此讨论了该分子体系的势能面静态特征.     

Cu吸附(SiO3)n(n=1—8)团簇几何结构和电子性质的密度泛函研究

运用密度泛函理论下的广义梯度近似和交换关联函数对Cu吸附(SiO₂)n(n=1—8)团簇的几何结构、电荷分布、稳定性和电子性质进行了较详细的研究,结果表明: Cu原子易于和带有悬挂键的Si原子作用并形成"铜岛膜"; Cu吸附(SiO₂)_n团簇后Si原子失去电子能力减弱,O原子得到电子能力增强;Cu(SiO₂)n(n 关键词： 密度泛函理论 2)_n (n=1—8)团簇')" href="#">Cu(SiO₂)_n (n=1—8)团簇 近红外吸收     

金属氢高温超导电性

本文利用晶体的平均电子半径r_s、离子质量M和声速v_j等较少参量表示Z价金属的有效声子谱α²F(ω)、电声子耦合常数λ和谱面积λ/2〈ω〉,并用Dynes的T_c公式,求得了金属氢、铅和铌的超导临界温度。计算表明,在零压下金属氢的λ=2.55,T_c=162K。 关键词：     

液晶N相→SA相转变点附近的反常粘滞系数

本文由粘滞系数的时间关联函数表达式,得到了实验观察到的现象:在液晶N相→S_A相转变点附近(T→T_(sA)),体粘滞系数的反常发散比切变粘滞系数反常发散要大得多。说明了Brochard等人的理论中,不能解释此实验的原因。 关键词：     

混合自旋反铁磁材料Y2BaNiO5的磁学和热力学性质

在格林函数的理论框架下，采用一维自旋为1的各向异性Heisenberg模型来讨论Y₂BaNiO₅材料的磁学和热力学性质.得到了它的自旋关联函数、低激发谱、基态能(E_g)、比热(C)和静态磁化率(χ)在不同交换各向异性因子下的性质，所得结果与实验和数值模拟结果完全一致. 关键词： Heisenberg模型 格林函数理论 Haldane能隙 反铁磁长程序     

摩擦颗粒体系各向同性压缩过程中的堵塞行为

利用分子动力学方法,模拟了5000个表面轻微摩擦(μ=1×10^-4)的弹性颗粒组成的体系在各向同性压缩过程中的堵塞(jamming)现象,研究了颗粒体系对边壁压强P和对关联函数第一个峰的高度g₁随体积分数φ的变化规律. 结果表明,当体系的体积分数φ大于临界体积分数φ_c时,P(φ)曲线表现出明显的黏滑(stick-slip)行为,法向的力-力关联函数、切向的力-力关联函数和颗粒的位置-位置关联函数同时发生跳变,说明宏观黏滑现象源自内部的力位形和几何构形的调整. 体系在φ缓慢增大过程中得到了不同的堵塞态,随着颗粒粒径的缓慢减小,体系得以松弛(unjamming),实现松弛过程并得到相应的φ_c. 对于不同堵塞态,其边壁压强P与φ-φ_c遵从幂律标度P∝(φ-φ_c)^0.964. 关键词： 堵塞相图 对关联函数 力-力关联函数 标度规律     

准一维体系的电子关联函数

对于具有库仑相互作用的准一维电子体系,本文根据电子气的集体振荡行为给出了该体系的多体波函数,并由此求出了准一维体系的电子关联函数g(|z₁₂|)。 关键词：     

Thermodynamics of an interacting Fermi system in the static fluctuation approximation

We suggest a new method of calculation of the equilibrium correlation functions of an arbitrary order for the interacting Fermi-gas model in the framework of the static fluctuation approximation method. This method based only on a single and controllable approximation allows obtaining the so-called far-distance equations. These equations connecting the quantum states of a Fermi particle with variables of the local field operator contain all necessary information related to the calculation of the desired correlation functions and basic thermodynamic parameters of the many-body system. The basic expressions for the mean energy and heat capacity for the electron gas at low temperatures in the high-density limit were obtained. All expressions are given in the units of r _s , where r _s determines the ratio of a mean distance between electrons to the Bohr radius a ₀. In these expressions, we calculate terms of the respective order r _s and r _s ². It is also shown that the static fluctuation approximation allows finding the terms related to higher orders of the decomposition with respect to the parameter r _s .     

准一维体系的电子关联的变分计算

对于具有库仑相互作用的准一维电子体系,本文提出了一种新的模型,得到了准一维体系的电子有效库仑势形式。在相关基函数理论框架下,根据电子气的集体振荡行为,给出该体系的多体波函数,并得到不同密度的电子体系的关联函数和关联能,本文得到的关联函数是恒正的,且满足归一化条件。     

Many-body effects in the binding energies of image states at surfaces

A study of the influence of many-body effects on binding energies and effective masses of image potential induced surface states is presented. The binding energies calculated using experimentally measured ε(ω) response functions show a dependence on the electron density different from that obtained using a plasmon model, and are in agreement with recent experimental data of diesen et al. [Phys. Rev. B33 (1986) 5241]. The effects of plasmon dispersion and single particle excitations on binding energies are evaluated with a simple model, and it is shown that they result in a strong cancellation in the range of r_s values where most experimental data have been obtained (r_s ≈ 3), if realistic values of the surface plasmon dispersion relation are used. Corrections to the effective masses due to many-body effects are shown to be of the order of 1%.     

Instability of layered quantum liquids: 1. Local-field correction in superlattices

For a superlattice with periodd the Singwi et al. (Phys. Rev.176, 589 (1968)) approach for the local-field correction and the static structure factor is formulated. With two approximations we reduce the resulting three-dimensional integral-equation into a one-dimensional integral-equation. For the local-field correction we present analytical results for small wave numbers and large wave numbers. An expression of Hubbard-typ is derived for the local-field correction. Explicit results for boson superlattices and electron superlattice are given. A charge-density-wave instability in a layered Bose condensate withr _s>r_scd^3/4 is discovered.r _s is the small parameter of the random-phase-approximation. The charge-density-wave instability is due to a many-body anomaly (short-range correlations) in layered structures and is a general property of layered quantum liquids. We find the charge-density-wave instability in a layered electron gas forr _s>r_scd. Double-quantum-well structures are also considered. The effects of a finite well width is calculated. The general implications of the charge-density-wave instability for microscopically layered quantum liquids are pointed out.     

半导体反型层中的电子关联和多体波函数

本文运用CBF(correlation basis function) 理论, 由电子间的有效势V_eff_(R) 和电子气的集体振荡行为, 给出准二维电子体系— 半导体反型层中的电子的关联因予U (R), 得到该体系的对关联函数、关联能和多体波函数. 关键词：     

Recurrence equations for the computation of correlations in the 1/r2 quantum many-body system

In a previous paper the two-particle distribution function and one-particle density matrix for the quantum many-body system with the 1/r ² pair potential have been expressed as limiting cases of Selberg correlation integrals. Recurrence equations are derived which allow rapid evaluation of these multidimensional integrals. The exact results for the two-particle distribution are compared with the harmonic approximation.     

Self-consistent Overhauser model for the pair distribution function of an electron gas at finite temperature

We present calculations of the spin-averaged pair distribution function g(r) in a homogeneous gas of electrons moving in dimensionality D=3 or D=2 at finite temperature. The model involves the solution of a two-electron scattering problem via an effective potential, which embodies many-body effects through a self-consistent Hartree approximation, leading to two-body wave functions to be averaged over a temperature-dependent distribution of relative momentum for electron pairs. We report illustrative numerical results for g(r) in an intermediate-coupling regime and interpret them in terms of changes of short-range order with increasing temperature.     

Spatial correlations in the electron gas: Path integral Monte Carlo simulation

Thermally excited states of the three-dimensional electron gas in a neutralizing background are computed by path integral Monte Carlo simulation for values of the Wigner-Seitz radius within the interval 5 < r _s < 15. Coulomb and exchange interactions, permutation symmetry, and spin state are treated explicitly. Variation of electron correlation functions with density and temperature is analyzed. Quantum effects suppress and enhance spatial correlation at low and high densities, respectively. Transition between the electron-gas states characterized by these opposite trends corresponds to a density of approximately 2.5 × 10²¹ cm^?3. A transition line between liquid-like and gaslike phases is determined in the temperature-density diagram. Weak anisotropy of many-body correlations in the liquid-like state stimulates excitation of spherically symmetric collective rotational modes. The effective short-range pseudopotential exhibits strong temperature dependence due to exchange effects. For strongly correlated systems, the characteristic screening length deviates from that predicted by the Thomas-Fermi screening model ( $ \sim \sqrt {r_s } $ ), approaching a linear function of r _s. The effective short-range interaction substantially differs from the Yukawa potential in mean field theory. Coulomb interaction shifts the Fermi level up by an order of magnitude or higher, and this effect becomes stronger with decreasing density.