[Phonopy-users] factor in phonon group velocity
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From: Liang C. <lia...@gm...> - 2015-10-13 08:03:23
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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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