As to which geom you use, it all depends on what you want to calculate.Usually people calculate Non-linear optical absorption properties, so I guess you want use opted GS.

• 拿计算三阶非线性极化率来说，计算公式里面需要用到不同激发态之间、激发态与基态之间的跃迁偶极矩，应该用哪一种结构作为初始构型来计算呢？