Dear DingWang Yuan,

It is not possible to calculate THG by finite difference techniques,
because all perturbing electric fields are frequency-dependent in
this case.

In a finite field method, at least one electric field will be static.

What you can calculate with ADF are, among other things:
- SHG (Second Harmonic Generation) analytically [beta tensor]
- EFISH (Electric-Field Induced SHG) by applying one finite electric
field [gamma tensor]
    by looking at the changes in the SHG beta-tensor.

In order to calculate THG a future ADF version would have to go one
order higher
in perturbation theory to obtain this quantity analytically.

Best regards,
Stan van Gisbergen

On Oct 13, 2004, at 2:45 AM, dwyuan_at_theory.issp.ac.cn wrote:

> Dear all,
>
> How to obtain the third harmonic generation (THG)
> using finite difference techniques?
>
>
> Thanks a lot in advance !
>
>
>
Dr. S.J.A. van Gisbergen      
Scientific Computing & Modelling NV
Theoretical Chemistry, Vrije Universiteit
De Boelelaan 1083
1081 HV Amsterdam
The Netherlands                              
T: +31-20-4447626    
F: +31-20-4447629        
vangisbergen_at_scm.com  
http://www.scm.com
Received on 2004-10-13 08:47:25