On the choice of coordinate origin in length gauge optical rotation calculations
On the choice of coordinate origin in length gauge optical rotation calculations
复制标题
长度计旋光计算中坐标原点的选择
DOI：
10.1002/chir.23575
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发表时间：
2023
期刊：
影响因子：
2
通讯作者：
Caricato, Marco
中科院分区：
文献类型：
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作者：
Parsons, Taylor;Balduf, Ty;Caricato, Marco
在这项工作中，我们用密度泛函理论(DFT)和耦合团簇理论(CC)中的标准近似方法研究了长度偶极规范(LG)中旋光(OR)计算中的原点依赖问题。我们使用我们最近提出的原点不变的LG(OI)方法作为计算的参考，并研究了是否可以适当地选择坐标原点和分子取向，使得LG-OR张量的对角元素与LG(OI)张量的对角元素相匹配。使用数值搜索算法，我们表明，在LG和LG(OI)结果匹配的情况下，可以找到多个空间方向。然而，一个简单的分析程序提供了一个空间方向，其中坐标系的原点靠近分子的质心。同时，我们也表明，对于每个分子来说，把原点放在质量中心并不是一个理想的选择(在我们的测试集中，OR的相对误差可以达到70%)。最后，我们证明了基于解析法的坐标原点的选择可以在不同的方法之间转换，并且它优于将原点放在质量中心或核电荷中心。这一点很重要，因为LG(OI)方法对于DFT来说是微不足道的，但对于CC家族中的非变分方法并不一定。因此，人们可以在DFT水平上确定最佳坐标原点，并将其用于标准LG-CC响应计算。
In this work, we explore the issue of origin dependence in optical rotation (OR) calculations in the length dipole gauge (LG) using standard approximate methods belonging to density functional theory (DFT) and coupled cluster (CC) theory. We use the origin‐invariant LG approach, LG(OI), that we recently proposed as reference for the calculations, and we study whether a proper choice of coordinate origin and molecular orientation can be made such that diagonal elements of the LG‐OR tensor match those of the LG(OI) tensor. Using a numerical search algorithm, we show that multiple spatial orientations can be found where the LG and LG(OI) results match. However, a simple analytical procedure provides a spatial orientation where the origin of the coordinate system is close to the center of mass of the molecule. At the same time, we also show that putting the origin at the center of mass is not an ideal choice for every molecule (relative errors in the OR up to 70% can be obtained in out test set). Finally, we show that the choice of coordinate origin based on the analytical procedure is transferable across different methods and it is superior to putting the origin in the center of mass or center of nuclear charge. This is important because the LG(OI) approach is trivial to implement for DFT, but not necessarily for nonvariational methods in the CC family. Therefore, one can determine an optimal coordinate origin at DFT level and use it for standard LG‐CC response calculations.