The role of self-consistency in double layer calculations

In a number of calculations involving nonlinear structures such as double layers and solitons, the Korteweg-de Vries theory is applied beyond its range of validity or approximations are made which are not self-consistent. Some situations arising in the theory of double layers in fluid multispecies plasmas are pointed out and attention is drawn to arbitrary-amplitude numerical calculations which yield results that are physically very different from those of the approximate theories. In particular, severe restrictions on the occurrence of ion-acoustic double layers in negative-ion plasmas and of electron-acoustic double layers in two-electron-component plasmas are found     

A method to estimate the self-consistency effects on electronic structure calculations

A simple method to estimate the effects of the self- -consistency on the calculation of the electronic structure of molecule and crystals is proposed. This procedure is based on the charge transfer between the constituent atoms and is intended to avoid much computational effort. Numerical results are presented for GaAs.     

Bulk modulus of alkali-halide mixed crystals

By using the bulk moduli of the pure and components we calculate, for various compositions, the isothermal bulk modulus of the following mixed crystals: NaCl-NaBr, KCl-KBr and KBr-Kl. The calculated values are in good agreement with the most recent experimental data.     

Bulk modulus and microhardness of tetrahedral semiconductors

Using the plasma oscillations theory of solids, simple relations have been proposed for the calculation of bulk modulus (B) and microhardness (H) of group IV, II-VI, III-V, I-III-VI₂ and II-IV-V₂ semiconductors with tetrahedral structure. We find that B=K₁ (?ω_p)^2.3333 and H=K₂ (?ω_p)^2.3333−K₃, where K₁, K₂ and K₃ are the constants. The numerical values of K₁, K₂ and K₃ are respectively, 0.141, 0.036 and 12.895 for group IV, 0.109, 0.0037 and 0.782 for II-VI, 0.125, 0.0202 and 5.743 for III-V, 0.109, 0.0065 and 1.160 for I-III-VI₂, and 0.125, 0.0359 and 15.310 for II-IV-V₂ semiconductors. The calculated values of B and H are compared with the experimental values and the values reported by different workers. Reasonably good agreement has been obtained between them.     

Methods for perturbation calculations in gravity

We show that gravitation, regarded as a self-interacting, massless spin-2 field theory, gives rise to a calculable perturbation expansion.     

Bulk modulus and its pressure derivatives of cuprous halides

The ab initio pseudopotential approach to the total crystal energy is presented using local DF formalism. The expressions for bulk modulus, its first and second pressure derivatives for group I-VII semiconductor binary compounds are derived. The expression for the second pressure derivative of the bulk modulus for four-fold crystal structures is derived for the first time within the pseudopotential framework. The computed results of the bulk modulus for cuprous halides are very close to the available experimental data.     

Unitary pole approximation andt-matrix perturbation theory in triton calculations

We find that the quality of the fits of the UPAt-matrix to the exactt-matrix for a given potential do not depend strongly on specific features, such as locality or inclusion of spin orbit forces in the potential. The accuracy of the UPA fits suggests the employment oft-matrix perturbation theory in triton ground state calculations. The accuracy of first ordert-matrix perturbation theory is satisfactory for the rank two separable tensor Tabakin potential.     

Double perturbation calculations of spin-spin coupling constants using localized orbitals

The Fermi contact contribution to N.M.R. spin-spin coupling constants has been calculated to the fourth order by a double perturbation development starting from a fully localized determinant, according to the assumptions of the PCILO-CNDO method. The use of diagrammatic techniques greatly simplifies the evaluation. There is a cancellation of certain types of diagram. The coupling constant between bonded atoms appears in the second order through a contribution which only depends on the appropriate bond orbital. The next orders involve the other bonds and correlation effects. For nonbonded atoms, the first contribution appears in the fourth order and results from direct delocalization through space, involving only the bonds on the two atoms.

An analytical and numerical comparison with previous calculations is performed for H-H and C-H coupling constants on small organic molecules. The relative importance of the various processes is discussed for the J _HH vicinal coupling constants of ethylene.     

BSSE-free second order intermolecular perturbation theory II. Sample calculations on hydrogen-bonded complexes

The second order BSSE-free intermolecular perturbation theory based on the ‘Chemical Hamiltonian Approach’ (CHA), which was developed in the first part of this paper is applied to several hydrogen bonded systems using a variety of different basis sets. The results show that the second order BSSE-free interaction energy is remarkably close to that obtained by the conventional MP2 interaction energy if the latter is properly CP corrected. This shows that these two independent and conceptually different approaches–the classical Boys-Bernardi scheme and the CHA method–strongly corroborate each other.     

Nonperturbative calculations in the framework of variational perturbation theory in QCD

Physics of Atomic Nuclei - We discuss applications of the method based on the variational perturbation theory to perform calculations down to the lowest energy scale. The variational series is...     

Breit-Pauli and direct perturbation theory calculations of relativistic helium polarizability.

Large Gaussian-type geminal wave function expansions and direct perturbation theory (DPT) of relativistic effects have been applied to calculate the relativistic contribution to the static dipole polarizability of the helium atom. It has been demonstrated that DPT is superior for this purpose to traditional Breit-Pauli calculations. The resulting value of the molar polarizability of 4He is 0.517254(1) cm3 x mol(-1), including a literature estimate of QED effects. As a by-product, a very accurate value of the nonrelativistic helium second hyperpolarizability, gamma = 43.104227(1) atomic units (without the mass-polarization correction), has been obtained.     

A second-order perturbation method for potential calculations in non-homogeneous conducting layers

A second-order perturbation method is presented to calculate the influence of the non-homogeneous conductivity on the potential distribution in a conducting layer. The method is illustrated by resistance measurements on a rectangular geometry.     

基于环境扰动的线性匹配场处理方法

匹配场处理面临的挑战主要是拷贝场失配。常规线性匹配场处理方法虽然对失配较宽容,但旁瓣较高,定位正确率依赖于失配的程度,且很容易受到强干扰的影响而失效。自适应匹配场处理可以获得较高的定位精度和旁瓣抑制性能,但环境参数失配、距离/深度空间欠采样、基阵及环境的波动所造成的误差等因素,均会导致其性能严重下降。环境扰动约束可提高自适应匹配场处理器的稳健性,基于这种思想,提出了基于环境扰动的线性匹配场处理方法,它不仅在环境失配的条件下比常规线性方法的定位正确率更高,而且在阵列采样数据存在幅度与相位随机误差的条件下,比自适应匹配场方法的稳健性更强.针对环境失配条件下的强干扰问题,还提出了一种线性匹配场干扰抑制算法,可有效地抑制水面干扰。典型浅海环境下的数值仿真和实测数据分析验证了方法的有效性.     

基于卟啉化合物的异质结有机太阳能电池

采用混合溶剂制备了四苯基卟啉(TPP)及其铜配合物(TPPCu)和氯化对甲氧基四苯基铁卟啉(TMPPFeCl),将三种卟啉化合物和富勒烯的衍生物(PCBM)分别共混,制备异质结太阳能电池。器件结构是ITO/porphyrin∶PCBM/Al,研究此类电池的性能。结果显示基于TPP∶PCBM的器件性能最优,其短路电流密度(JSC)是0.98mA.cm-2,开路电压(VOC)是0.52V,填充因子(FF)为30.1%。TPP是三种卟啉化合物中最佳的给体材料。进而考察了TPP∶PCBM的不同浓度配比对器件性能的影响。TPP∶PCBM的最佳浓度配比为1∶1,增加或减少TPP的量都会使器件的短路电流和开路电压降低,对填充因子的影响不大。