[Q-e-developers] Strange problem in the calculation of monolayer InSe with QE

[jinlong.ma.dr at szu.edu.cn]

Dears,

    I am a user of Quantum Espresso v6.0 ( QE6.0 ). Now I am using QE6.0 to calculate the phonon dispersion of monolayer InSe, however, a strange problem occurs. As InSe is a polar material, the original interatomic force constants (IFCs) contain dielectric tensor and born charge. With this orignal IFCs, the phonon dispersion agrees well with other QE or VASP results, as shown in the black solid line (with polar) of attached "InSe_phonon.jpg'.

 

   Then I try to find out the effect of polar part by removing the dielectric tensor, born charge and setting "T" to "F" in the IFCs. Consequently, the phonon dispersion becomes very very bad, showing great influence from polar part among all the Brillouin Zone [red dash line (without polar) of attached "InSe_phonn.jpg']. This disobeys to our common opinion that the effect of polar should not be so large and span to all the Brillouin Zone, which has been confirmed from VASP calculation of InSe. When we transform the IFCs of QE to VASP formation, the result is also bad.

 

   We suspect that is there some bugs in the QE6.0 for the calculation of two-dimensional polar meteral? We cannot find the reason, can you give a help? The input files of InSe is also attached as "InSe_phonon.zip".

 

   Thanks in advance. We are looking forward your kind response.

 

Jinlong Ma,


Postdoctoral Researcher ,
Institute for Advanced Study,
Shenzhen University,

Nanhai Avenue 3688,
Nanshan District,
Shenzhen,Guangdong, 
China,518060

     

 
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