Re: [Phonopy-users] factor in phonon group velocity

[Atsushi T. <atz...@gm...>]

Hi,

Unit conversion and 2pi factor are tricky. Unless your values used for this
calculation, it's difficult to answer.

Togo

On Tue, Oct 13, 2015 at 5:03 PM, Liang Chen <lia...@gm...>
wrote:

> Dear Phono3py users,
>
> I am using VASP and phono3py to determine the thermal conductivity of GaN.
> I output the frequencies, group velocities, etc. I am confused about the
> 2pi factor for phonon group velocity.
>
> In the manual, it is said the units of group velocity are The physical
> unit is [image: \text{THz}\cdot\text{\AA}] (without [image: 2\pi]).
> However, I calculated the group velocity manually from d_omega/d_q where
> omega is frequency*2pi, and q is calculated from reciprocal lattice vectors
> and 2pi/lattice_constant. The calculated value is same to the output
> directly from phono3py. According to the manual, the calculated value
> should be equal to the output times 2pi? Did I have any mistake here in my
> calculation of group velocity? Thank you. I will appreciate any comment or
> discussion.
>
> Regards,
>
>
> Liang Chen
> Xi'an Jiaotong University
> School of Energy and Power Engineering
> 28 Xianning Road, Xi'an, Shaanxi 710049, China
>
>
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-- 
Atsushi Togo
http://atztogo.github.com/
atz...@gm...