Wrong phonon band interpolation
Posted: Wed Feb 05, 2020 5:28 pm
Dear EPW users,
When I try to calculate the electron-phonon couplingconstant for CuSbTe2, negative phonon frequencies appear. However, the electronic band structure is correctly interpolated by wannier. The weird negative frequencies appear when "plotband = .true." is set to present the interpolated plot. While, I obtain positive frequencies from ph.x when PAW pseudopotentials were adopted. youcan see both figures extracted from EPW and ph.x from https://mega.nz/#F!nXI20QJI!JfFXMdY8Y-0cjjhDUs8-vw . On the other hand, other types of the pseudo (NC and US ) have predicted instability at specificq points (related to commensurate supercell). To verify the results and eliminate the discrepancy another code, VASP, was used. Both VASP and quantum espresso predict the same stable phonon dispersion using PAW pseudo. Do you have any idea about this problem? Can this problem arise from the choice of the PAW pseudo? May this problem be related to wannier projections?
When I try to calculate the electron-phonon couplingconstant for CuSbTe2, negative phonon frequencies appear. However, the electronic band structure is correctly interpolated by wannier. The weird negative frequencies appear when "plotband = .true." is set to present the interpolated plot. While, I obtain positive frequencies from ph.x when PAW pseudopotentials were adopted. youcan see both figures extracted from EPW and ph.x from https://mega.nz/#F!nXI20QJI!JfFXMdY8Y-0cjjhDUs8-vw . On the other hand, other types of the pseudo (NC and US ) have predicted instability at specificq points (related to commensurate supercell). To verify the results and eliminate the discrepancy another code, VASP, was used. Both VASP and quantum espresso predict the same stable phonon dispersion using PAW pseudo. Do you have any idea about this problem? Can this problem arise from the choice of the PAW pseudo? May this problem be related to wannier projections?