[Pw_forum] Nscf and scf

[Vo, Trinh (388C)]

Dear PWSCF Users,

I run the calculation for a system of 216 atoms (SiP).  The CPU time for the calculation of 4x4x4 kpt mesh, which actually did calculation for 24 kpts due to symmetry, is 1d4h18m (~28h).  When I performed a nscf calculation for 41kpts along 001 direction, the CPU time is 3d5h (~77h).  Thus, the time for one kpt in scf calculation is ~1.17h/kpt,  and 1.87h in nscf calculation.  I am wondering how can it take more time for nscf calculation than for scf calculation.  I don’t understand why.  Could you explain to me what can cause this to happen.  I use QE-4.1.2.

Thank you very much,

Trinh Vo
CalTech/JPL
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