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about the optical calculations in OpenMX3.9
Date: 2022/12/13 11:14
Name: Jian Zhou   <>

Dear Prof. Ozaki,

I have a question about the calculations of dielectric functions in OpenMX 3.9. I have tried to calculate the optical conductivity of metal material (such as Li, Na) and I set CDDF.material_type=1. I think OpenMX has added the Drude term in the calculation and my calculations confirm it by the rapid upturn in the imaginary part of the dielectric functions when the frequency approaches zero.

My question is how to adjust the parameter Gamma in the Drude term (e.g. Eqs. 3 and 4 in PRB 79, 125117 (2009), In my calculation, I find that the CDDF.FWHM keyword can be used to tune the smearing of the Drude term (intraband transitions) as well as the inter-band transitions. I wonder if it is possible to set the size of the smearing for the two terms (intraband and inter-band transitions) separately?

Thank you.

Best wishes,

Jian Zhou

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Re: about the optical calculations in OpenMX3.9 ( No.1 )
Date: 2022/12/15 10:48
Name: Yung-Ting Lee

Dear Prof. Jian Zhou,

Based on the Kubo-Greenwood formula, we implemented the frequency-dependent optical conductivity in OpenMX-3.9. The equation of frequency-dependent optical conductivity can be found in (1) Phys. Rev. B 98, 115115 (2018) and (2) Phys. Rev. B 102, 075143 (2020). Both of intraband and interband transitions are included in the equation of frequency-dependent optical conductivity. The way that I dealt with intraband transitions was written in section A. Optical Conductivity in the computational method in Phys. Rev. B 102, 075143 (2020).

For Q1:
The Drude term (e.g. Eqs. 3 and 4 in PRB 79, 125117 (2009)) is not included in OpenMX3.9. Therefore, there is no Gamma parameter.

The smearing parameter (or lifetime) in the Kubo-Greenwood formula is eta (one parameter) in Eq. 1 in Phys. Rev. B 98, 115115 (2018).

For Q2:
It is possible to set two different smearing parameters by using conditional expressions in the optical code. One is for intraband transitions and the other is for interband transitions. Of course, one needs to modify the optical code slightly for this purpose.

On the other hand, L. Calderin et al. have developed and implemented the Kubo-Greenwood formula for projector-augmented wave datasets for Quantum Espresso and published their excellent research work in Computer Physics Communications 221, 118-142 (2017). The paper is also a great reference for understanding the Kubo-Greenwood formula, intraband/interband transitions, and Drude components in section 2.2.

Best regards,
Yung-Ting Lee
Re: about the optical calculations in OpenMX3.9 ( No.2 )
Date: 2022/12/16 10:55
Name: Jian Zhou  <>

Dear Dr. Lee,

Thank you for your reply. I will read these papers carefully.

Best wishes,

Jian Zhou

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