论文标题
周期系统中的密度拟合：在钻石和氧化物中应用TDHF
Density fitting in periodic systems: application to TDHF in diamond and oxides
论文作者
论文摘要
基于exciton代码中的高斯轨道基础，描述并实现了基于BLOCH函数上库仑矩阵元素计算库仑矩阵元素的强大密度拟合方法。通过比较钻石，氧化镁和大块NE的SCF HF计算中的库仑和交换能量来测试该方法。将来自鲁棒方法的密度拟合系数与用于散装NE中波函数轨道产物的变异方法的系数进行比较。来自密度拟合的四个中心库仑基质元件应用于二氧化钛二氧化钛的钻石，氧化镁，氧化镁，氧化镁和金红石多型的时间依赖性的Hartree-fock（TDHF）计算。相对于被占用状态统一的虚拟状态向下转移，并在TDHF Hamiltonian中使用0.4的电子孔吸引项缩放，与实验和/或Bethe-Salpeter方程计算得出了良好的一致性。这种方法反映了相似的“剪刀”调整被占用状态和虚拟状态的调整，并在某些时间依赖于DFT计算中引入了缩放的电子孔吸引项。
A robust density fitting method for calculating Coulomb matrix elements over Bloch functions based on calculation of two- and three-center matrix elements of the Ewald potential is described and implemented in a Gaussian orbital basis in the Exciton code. The method is tested by comparing Coulomb and exchange energies from density fitting to corresponding energies from SCF HF calculations for diamond, magnesium oxide and bulk Ne. Density fitting coefficients from the robust method are compared to coefficients from a variational method applied to wave function orbital products in bulk Ne. Four center Coulomb matrix elements from density fitting are applied to time dependent Hartree-Fock (TDHF) calculations in diamond, magnesium oxide and anatase and rutile polytypes of titanium dioxide. Shifting virtual states downwards uniformly relative to occupied states and scaling the electron-hole attraction term in the TDHF Hamiltonian by 0.4 yields good agreement with either experiment and/or Bethe-Salpeter equation calculations. This approach mirrors similar 'scissors' adjustments of occupied and virtual states and introduction of a scaled electron-hole attraction term in some time dependent DFT calculations.
