DingWang Yuan,

Just as an addition to the comments by Stan.

If you are interested in THG at low frequencies you can fit the EFISH
results to a dispersion formula and use this to obtain an estimate for
the THG. See e.g. van Gisbergen et al. Phys. Rev. Lett. 78, 3097-3100
(1997)

Best wishes,

Lasse

Stan van Gisbergen wrote:

> 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 18:27:55