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<div><span></span><span style="font-family: "Microsoft YaHei UI", Tahoma;">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 "</span><span style="background-color: transparent;"><font face="Microsoft YaHei UI, Tahoma">S matrix not positive definite</font></span><span style="background-color: transparent;"><font face="Microsoft YaHei UI, Tahoma">", what cause it happend? I have tried to increase the energy cutoff, but nothing changed. So, has anyone encountered this problem too? C</font></span><span style="background-color: transparent;"><font face="Microsoft YaHei UI, Tahoma">an someone give me some advice?</font></span></div><div><span style="background-color: transparent;"><font face="Microsoft YaHei UI, Tahoma"><br></font></span></div><div><span style="font-family: "Microsoft YaHei UI", Tahoma;">Best wishes,</span></div><hr style="width: 210px; height: 1px;" color="#b5c4df" size="1" align="left">
<div><span><div style="MARGIN: 10px; FONT-FAMILY: verdana; FONT-SIZE: 10pt"><p style="margin-top: 0px; margin-bottom: 0px; font-size: 14px; font-family: "Microsoft YaHei UI", Tahoma;">Jianguo Si (jgsi@foxmial.com)<br>China Spallation Neutron Source<br>Dongguan Campus, <span style="background-color: transparent;">Institute of High Energy Physics, Chinese Academy of Sciences</span></p><p style="margin-top: 0px; margin-bottom: 0px; font-size: 14px; font-family: "Microsoft YaHei UI", Tahoma;">A2-524, Zhongziyuan road NO.1, Dongguan, Guangdong, PR China. 523803<br>Tel: 86-769-89156106</p></div></span></div>
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