this error used to appear frequently because of the conjugate gradient method used to get the ground state wavefunctions (iscf 5). It means that the CG solver is stuck, and a quadratic fit to the energy cannot find a reasonable prediction for the next SCF step (after 13 tries) and it stops.

This has been superseded by iscf 7 (the default) which never gets into this state. Use that instead. For PAW potentials use the default iscf 17 (basically you can always leave out iscf - the default is the best).

Matthieu

hello

I ran rf1 lesson for LaCoO3

my input variables are:

# Crystalline LaCoO3(cubic) : computation of the total energy

#

#Specific to ground state calculation

kptopt 1

tolvrs 1.0d-18

iscf 5

#######################################################################

#Common input variables

#Definition of the unit cell

acell 3*7.22

rprim 1.0 0.0 0.0

0.0 1.0 0.0

0.0 0.0 1.0

#Definition of the atom types

ntypat 3

znucl 57 27 8

#Definition of the atoms

natom 5

typat 1 2 3 3 3

xred

0.0 0.0 0.0

0.5 0.5 0.5

0.5 0.5 0.0

0.5 0.0 0.5

0.0 0.5 0.5

#Gives the number of band, explicitely (do not take the default)

nband 15

#Exchange-correlation functional

ixc 1

#Definition of the planewave basis set

ecut 55.0

#Definition of the k-point grid

kptrlatt -4 4 4

4 -4 4

4 4 -4

#Definition of the SCF procedure

nstep 55

diemac 9.0

and the error in log file is:

,Min el dens= 7.6096E-05 el/bohr^3 at reduced coord. 0.0000 0.0000 0.0000

,Max el dens= 1.3258E+00 el/bohr^3 at reduced coord. 0.5600 0.5600 0.5600

rhohxc_coll : enter with option, nspden 1 1

ETOT 46 -85.312003083360 -8.606E-05 1.641E-04 1.992E-01 0.000E+00 0.000E+00

scprqt: <Vxc>= -4.3537831E-01 hartree

findmin : lambda_predict -7.9456E-02 etotal_predict -8.5312079788E+01

scfcge : ERROR -

Potential-based CG line minimization not converged after 13 restarts.

Action : read the eventual warnings about lack of convergence.

Some might be relevant. Otherwise, raise nband.

leave_new : decision taken to exit ...

1

and if I increase the nband, in 3rd program in rf1 lesson an error occurs because of this increasing.

how can I solve this problem?

thanks