[QE-users] S matrix not positive definite

[jgsi at foxmail.com]

Hello everyone.  I am proforming a phonon dispersion calculations based on DFPT via the ph.x code. When the calculation comes to the second q-point (not the Gamma point),  the code sent a error message of "S matrix not positive definite", what cause it happend? I have tried to increase the energy cutoff, but nothing changed.  So, has anyone encountered this problem too?  Can someone give me some advice?

Best wishes,


Jianguo Si (jgsi at foxmial.com)
China Spallation Neutron Source
Dongguan Campus, Institute of High Energy Physics, Chinese Academy of Sciences
A2-524, Zhongziyuan road NO.1, Dongguan, Guangdong, PR China. 523803
Tel: 86-769-89156106
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