The way quantum mechanical ab initio computer codes allow to compute, through perturbation theory (the so-called SC-CP, self-consistent coupled-perturbed scheme), many properties resulting from the interaction of the electric field with a crystalline system is illustrated. The polarizability, which leads to the dielectric tensors as well as to the refractive indices and to the birefringence of materials, is the simplest on this list. Higher order tensors, like the first and second hyperpolarizabilities, can be obtained as well with the CRYSTAL code here used. These properties, resulting from the Taylor expansion of the total energy of the solid as a function of the electric field, belong to a large family of phenomena generated by combining in different ways the frequencies of the fields. Second-harmonic generation (SHG), Pockels effect, intensity-dependent refractive index (IDRI), and other quantities now accessible to experiment can be computed at a relatively low cost and with high accuracy.

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从介电张量的各向异性到双折射：量子力学方法

量子力学从头算起的计算机代码允许通过扰动理论（所谓的SC-CP，自洽耦合扰动方案）计算出电场与晶体系统相互作用产生的许多特性。极化率是该列表中最简单的，它导致介电张量，折射率和材料的双折射。像第一和第二超极化率一样，高阶张量也可以通过此处使用的CRYSTAL代码获得。由固体的总能量的泰勒膨胀随电场的变化而产生的这些性质属于通过以不同方式组合电场频率而产生的大量现象。二次谐波（SHG），普克尔斯效应，