# How to correct units in the band.yaml file of QE, to band.yaml of VASP

I see from the phonopy web page 1 that the physical unit systems used for the calculators are different for different codes 1. On the same page, it is mentioned that "For these sets of physical properties, phonon frequency is calculated in THz." Does it mean that the final unit for frequency and group velocity in band.yaml and gruneisen.yaml for VASP and QE codes are the same?

I was told by Prof. Togo, the developer of phonopy, that the unit of frequency is considered the same in VASP and QE, but that of group velocity is not.

Could someone please help me: how can I convert the unit of velocity in the QE band.yaml file to the units of the VASP band.yaml format (THz/Angstrom).

The unit in the VASP band.yaml file is THz/Angstrom while in the band.yaml file of QE it may be in THz/Bohr (not sure). To make the QE format of band.yaml into VASP band.ymal, can we do the conversion like below?

1bohr = 0.529177249 Angstrom
1/bohr = 1/0.529177249 = 1.88972598857


So I need to multiply the velocity in band.yaml of QE by 1.88972598857?

My half-finished conversation on the phonopy mailing list can be found here 2

An example of the VASP band.yaml and QE band.yaml can be found here 3.

• +1. Welcome to our new community and thank you for contributing this question here! We hope to see much more of you in the future !!! We also have chat rooms for phonopy, for VASP, and for QE. Can you say "hello" to us in those rooms so that we remember you're interesting in those programs? Aug 9 at 16:22
• Finally your we.tl requires us to accept cookies and some terms and conditions. Could you instead put all files relevant to this question in this GitHub repository in a folder called 6537 since 6537 is the number in the URL of this question? If you have any trouble, perhaps let me know your GitHub username and I can try to help you. Aug 9 at 16:23
• Thanks Nike, this is a very unique update. I will drop everything here. I am busy for a meeting. So, I will update the things tomorrow.
– kcb
Aug 10 at 16:59
• Have you had time now to make that update to the question? Thanks! Aug 21 at 18:11
• Actually, I am understanding the quantum espresso format. I will update it once I finish that.
– kcb
Aug 22 at 7:43