negative phonon modes in el-ph calculation

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negative phonon modes in el-ph calculation

Postby sdwang » Tue Dec 12, 2017 8:31 am

Dear developers,
I have calculate the phonons under the input file od 02ph.in, but the lowest 3 branches are negative at gamma point. Does this affect the final
results? If so, how could we avoid it.
Thanks!
S. D. Wang
IMU,HOHHOT,CHINA
E-mail: sdwang@imu.edu.cn
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Posts: 202
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Re: negative phonon modes in el-ph calculation

Postby amolina » Sun Jan 21, 2018 11:44 am

Hi,
the example for phonons in yambopy is a non-converged test. Therefore the user must check the convergence parameters for getting reliable results. In addition, the acoustic phonons, the 3 lowest branches at gamma can have negative values. One solution is to apply the acoustic sum rule with the functions designed for that in Quantum Espresso (dynmat.x).

Best,

Alejandro


PS: Can you update your profile to include your signature?
Alejandro Molina-Sánchez
Physics and Materials Research Unit
Campus Limpertsberg
Université du Luxembourg
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