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首页> 外文期刊>The Journal of Chemical Physics >Accurate density functional calculations on frequency-dependent hyperpolarizabilities of small molecules
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Accurate density functional calculations on frequency-dependent hyperpolarizabilities of small molecules

机译：小分子随频率变化的超极化率的精确密度泛函计算

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In this paper we present time-dependent density functional calculations on frequency-dependent first (beta) and second (gamma) hyperpolarizabilities for the set of small molecules, N-2, CO2, CS2, C2H4, NH3, CO, HF, H2O, and CH4, and compare them to Hartree-Fock and correlated ab initio calculations, as well as to experimental results. Both the static hyperpolarizabilities and the frequency dispersion are studied. Three approximations to the exchange-correlation (xc) potential are used: the widely used Local Density Approximation (LDA), the Becke-Lee-Yang-Parr (BLYP) Generalized Gradient Approximation (GGA), as well as the asymptotically correct Van Leeuwen-Baerends (LB94) potential. For the functional derivatives of the re potential the Adiabatic Local Density Approximation (ALDA) is used. We have attempted to estimate the intrinsic quality of these methods by using large basis sets, augmented with several diffuse functions, yielding good agreement with recent numerical static LDA results. Contrary to claims which have appeared in the literature on the basis of smaller studies involving basis sets of lesser quality, we find that the static LDA results for beta and gamma are severely overestimated, and do not improve upon the (underestimated) Hartree-Fock results. No improvement is provided by the BLYP potential which suffers from the same incorrect asymptotic behavior as the LDA potential. The results are however clearly improved upon by the LB94 potential, which leads to underestimated results, slightly improving the Hartree-Fock results. The LDA and BLYP potentials overestimate the frequency dependence as well, which is once again improved by the LB94 potential. Future improvements are expected to come from improved models for asymptotically correct exchange-correlation potentials. Apart from the LB94 potential used in this work, several other asymptotically correct potentials have recently been suggested in the literature and can also be expected to improve considerably upon the relatively poor LDA and GGA results, for both the static properties and their frequency dependence. (C) 1998 American Institute of Physics. [S0021-9606(98)30547-4]. [References: 69]
机译：在本文中，我们针对一组小分子N-2，CO2，CS2，C2H4，NH3，CO，HF，H2O，与频率相关的第一和第二个超极化率，提供了随时间变化的密度泛函计算和CH4，并将其与Hartree-Fock和相关的从头算计算以及实验结果进行比较。研究了静态超极化率和频率色散。使用了三个与交换相关（xc）势有关的近似值：广泛使用的局部密度近似值（LDA），Becke-Lee-Yang-Parr（BLYP）广义梯度近似值（GGA）以及渐近正确的Van Leeuwen -Baerends（LB94）的潜力。对于势能的函数导数，使用绝热局部密度近似（ALDA）。我们试图通过使用大的基集来估计这些方法的内在质量，这些基集用多个扩散函数进行了扩充，与最近的静态LDA数值相吻合。与基于较小质量基础集的较小研究在文献中提出的主张相反，我们发现β和γ的静态LDA结果被严重高估了，而Hartree-Fock结果（被低估了）没有改善。 BLYP电位并没有提供与LDA电位相同的不正确渐近行为的改善。但是，LB94电位明显改善了结果，导致结果被低估，从而略微改善了Hartree-Fock结果。 LDA和BLYP电位也高估了频率依赖性，而LB94电位又再次提高了频率依赖性。预期未来的改进将来自渐近正确的交换相关电位的改进模型。除了这项工作中使用的LB94电位以外，最近在文献中还提出了其他几种渐近正确的电位，并且在静态特性及其频率依赖性方面，相对较差的LDA和GGA结果也有望大大提高。 （C）1998美国物理研究所。 [S0021-9606（98）30547-4]。 [参考：69]

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