[Pw_forum] the procedure of calculating the Raman tensor using the finite electric field method

[li niu]

Dear all.
Thanks for your advice!
I'm sure that the positions from CPMD are correctly passed to the scf code because
I have checked the input geometry using xcrysden. The atomic positions of *.xyz file from 
CPMD are the same with positions in the case of xcysden-display-unit of repetition-translational
asummetric unit.
And the microstructures,electric structures and optical properties of this semiconductor model 
have been analyed and published.  
Why are the forces and stress so big?
I should use vc-relax (pw.x code) to compute the equilibrium geometry 
before running finite electric field method to calculate Raman tensor. Is it right?
  Bests,
   
  Niu Li
Harbin Institute of Technology
China


       
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