[QE-users] SCF energy rise up from iteration 2

[Rameswar Bhattacharjee]

Hi Everyone,
I am doing a single-point calculation on a 1D polymer in QE using PBE-PAW.
However, I am seeing an issue in the SCF iteration cycles. The first
iteration seems to print the right electronic energy but from iteration 2
the energy suddenly increases significantly and then the SCF ends up with
higher energy. I am a little confused about how to stabilize the SCF
iteration so the energy does not go up. Any suggestions will be highly
appreciated.

I am providing the output of the first three iterations of the SCF for deep
insights.

------------------------------------------------------------------------------

     iteration #  1     ecut=   120.00 Ry     beta= 0.30

     Davidson diagonalization with overlap

     ethr =  1.00E-02,  avg # of iterations =  2.0


     negative rho (up, down):  1.348E-04 0.000E+00


     total cpu time spent up to now is       13.7 secs


     total energy              =    -304.41586797 Ry

     estimated scf accuracy    <       2.72932626 Ry


     iteration #  2     ecut=   120.00 Ry     beta= 0.30

     Davidson diagonalization with overlap

     ethr =  3.79E-03,  avg # of iterations =  1.0


     negative rho (up, down):  1.006E-04 0.000E+00


     total cpu time spent up to now is       16.3 secs


     total energy              =    -304.13553253 Ry

     estimated scf accuracy    <       0.76532583 Ry


     iteration #  3     ecut=   120.00 Ry     beta= 0.30

     Davidson diagonalization with overlap

     ethr =  1.06E-03,  avg # of iterations =  6.0


     negative rho (up, down):  5.328E-05 0.000E+00


     total cpu time spent up to now is       19.4 secs


     total energy              =    -304.26340272 Ry

     estimated scf accuracy    <       0.08826578 Ry
--------------------------------------------------------------------------------------------

Thanks
Rameswar Bhattacharjee
Georgetown University
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