# [Pw_forum] Davidson diagonalization with overlap

Cao TF tfcao at theory.issp.ac.cn
Tue Nov 15 09:14:45 CET 2011

```Dear QE users
I am relaxing the structure of graphene with hydrogen adsorbed on it. But in iteration there is " Davidson diagonalization with overlap".  What can be the reasons?  And how to solve it . Any suggestions will be appreciated.
Here is part of the  out file:
Writing output data file graphene.save
NEW-OLD atomic charge density approx. for the potential

total cpu time spent up to now is 127989.94 secs

per-process dynamical memory:   116.7 Mb

Self-consistent Calculation

iteration #  1     ecut=    30.00 Ry     beta=0.70
Davidson diagonalization with overlap
ethr =  1.00E-06,  avg # of iterations =  4.0

total cpu time spent up to now is 129567.23 secs

total energy              =   -1141.65432551 Ry
Harris-Foulkes estimate   =   -1141.65612583 Ry
estimated scf accuracy    <       0.00636573 Ry

iteration #  2     ecut=    30.00 Ry     beta=0.70
Davidson diagonalization with overlap
ethr =  1.58E-06,  avg # of iterations =  2.0

total cpu time spent up to now is 130246.48 secs

total energy              =   -1141.65417045 Ry
Harris-Foulkes estimate   =   -1141.65465073 Ry
estimated scf accuracy    <       0.00113580 Ry

iteration #  3     ecut=    30.00 Ry     beta=0.70
Davidson diagonalization with overlap
ethr =  2.83E-07,  avg # of iterations =  2.7

total cpu time spent up to now is 131108.66 secs

total energy              =   -1141.65435750 Ry
Harris-Foulkes estimate   =   -1141.65436350 Ry
estimated scf accuracy    <       0.00002145 Ry

iteration #  4     ecut=    30.00 Ry     beta=0.70
Davidson diagonalization with overlap
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T.F.Cao  DFT and phonon physics
======================================================================
Add: Research Laboratory for Computational Materials Sciences,
Instutue of Solid State Physics,the Chinese Academy of Sciences,
P.O.Box 1129, Hefei 230031, P.R.China
Tel: 86-551-5591464-326(office)
Fax: 86-551-5591434

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