The energy is variational, that is: it goes down as self-consistency is
approached. The energy term that makes the energy variational is however
approximate and becomes exact only at self-consistency. As a consequence
it may happen that at the beginning of the self-consistency the energy
goes up instead of going down. Nothing to worry about as long as the
energy eventually converges (monotonically from above)
Paolo
On 18/12/2022 19:23, Rameswar Bhattacharjee wrote:
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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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_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list [email protected]
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