The ABINIT Users Mailing List ( CLOSED )

["Wu Rongqin" <g0203654@nus.edu.sg>]

Dear Dr Gonze,
 
I am fully aware that the mechanism of nonlinear optics in the very low 
frequency is quite from that for visible range. Actually for linear response, 
only the former can be obtained, right? because in the visible range, 
nonlinear as well as linear, is related to the properties of excitation 
states, which goes beyond lda, rhgit? But as for very low frequency, the 
perturbation only causes electronic polarization, right?

I tried but I got a negative nonlinear coefficient for ZnO, is this physical? 
I do not know why.

I tested different ixc for the same pps and found that the results differ 
very little. Is this normal?

Rongqin Wu 
-----Original Message-----
From: Xavier Gonze [mailto:gonze@pcpm.ucl.ac.be] 
Sent: 2004年8月25日 20:54
To: forum@abinit.org
Subject: Re: [abinit-forum] help about pp

Wu Rongqin wrote:
> Dear all,
> 
>  
> 
> I want to do nonlinear optics calculation. Abinit can now do only when 
> ixc=3 or 7. but very few pseudopotentials are made from such ex-co 
> function. So if the pps have different pspxc from 3 or 7, can they be 
> used to do nonlinear optics calculation by setting ixc=3 or 7?

Dear Wu Rongqin,

Just to be sure : are you interested in low-frequency non-linear
responses (like electrooptic coefficients, that include the phonon
contributions, but for frequencies << 1 eV),
or in responses to electro-magnetic radiations in the visible range ?

Electro-optic coefficients are present in v4.3 , however
with restricted ixc choice. You might test the sensibility
to ixc choice by changing it for linear responses... Still,
this would not guarantee that the answer is sufficiently accurate
for your purpose.

In the latter case (visible range), some capabilities (sum-over-states)
are present in v4.4 (thanks to S. Sharma, helped by M.Verstraete),
to be available soon, but nothing in v4.3 .
All ixc choices will be allowed.

Xavier Gonze