I have been trying to calculate the dielectric function of HgS. After checking convergence, I did plot the real and the imaginary part of the dielectric function and the agreement with experiment is very good EXCEPT that at low energies I am getting unusual results. The imaginary part becomes negative, while it should go to zero. At the same time, the real part is going upward when it should got downward. I did check K point convergence as well as Ecut and the result does not change. I think this results is unphysical, basically because if the Img and real part are related through the Kramers-Kroning relation and if the Imag should go to zero, then the Real part should also go to zero. Is there anything I am missing in the calculation? is the a way within Abinit to avoid this problem?
Thanks a lot!
Unusal results in optic calculation
Moderators: MMNSchmitt, gonze
Re: Unusal results in optic calculation
That is very strange.
Which program are you using for the optical spectra?
There are several ways in abinit to get it,
In NC pseudo-potentials, you can use:
optics, conducti or the gw code, there are also external codes as Yambo and DP.
They all in principle should give the same result.
But, you could make a test with another program, to see if the error is related to the program you are using
or to the groud state calculation.
Best
Tonatiuh
Which program are you using for the optical spectra?
There are several ways in abinit to get it,
In NC pseudo-potentials, you can use:
optics, conducti or the gw code, there are also external codes as Yambo and DP.
They all in principle should give the same result.
But, you could make a test with another program, to see if the error is related to the program you are using
or to the groud state calculation.
Best
Tonatiuh
Tonatiuh Rangel
Re: Unusal results in optic calculation
Dear Tonatiuh,
let me spell a bit more what is my problem.
I did use the optics code by following the tutorial and changing the variables to fit my problem. In my case, I did have to use
the scissor operator to match the electronic band gap. After the calculation, the agreement with experiment
is really good but as I said, the only thing that I do not like is that the imaginary part of the dielectric
function should be zero up to 1.2 eV and in my case it becomes negative (just a tiny bit) and the real part should decrease
and it increases. In order to check if the problem comes from some type of convergence, I did massage the data and put
at hand zeroes on the imaginary part. By using the Kramers-Kroning relation I was able to obtain the right behavior on the real part.
I will try the Yambo code..
Thanks!
let me spell a bit more what is my problem.
I did use the optics code by following the tutorial and changing the variables to fit my problem. In my case, I did have to use
the scissor operator to match the electronic band gap. After the calculation, the agreement with experiment
is really good but as I said, the only thing that I do not like is that the imaginary part of the dielectric
function should be zero up to 1.2 eV and in my case it becomes negative (just a tiny bit) and the real part should decrease
and it increases. In order to check if the problem comes from some type of convergence, I did massage the data and put
at hand zeroes on the imaginary part. By using the Kramers-Kroning relation I was able to obtain the right behavior on the real part.
I will try the Yambo code..
Thanks!