[SIESTA-L] How to add nonlinear external potential to Siesta calculation

[Jingbin Li]

Hi Everyone,
 I am wondering is there a way to add nonlinear extermal potential to Siesta
calculation?
For example, I have a potetnial in form of V_{ext} = a_{0} + a_{1}* x +
a_{2}*x^{2} + a_{3}*x^{3}.
Here x is the X axis coordiante. Thanks.

Best,
Jingbin