[Q-e-developers] Questions about BFGS

[Chen (Bonnie) Wang]

Hi,

I am an undergrad at MIT doing research regarding an orthorhombic BaCeO3
crystal structure (please see below for the input file). I have been trying
to find the ground state energy for the unit cell, but my output files have
not given me the final energies, and these errors below show up.

*Input: *

&CONTROL
 calculation = "relax"
 restart_mode = "from_scratch"
 verbosity = "low"
 outdir = "./tmp/"
 pseudo_dir = "./"
 etot_conv_thr = 1.0D-5
 forc_conv_thr = 1.0D-6
 max_seconds = 172800.0
 nstep = 500
/
&SYSTEM
 ibrav = 0
 ntyp = 3
 nat = 20
 tot_charge = 0.0
 ecutwfc   = 165.D0
 ecutrho = 1320.D0
/
&ELECTRONS
 electron_maxstep = 500
 conv_thr    = 1.D-5
/
&IONS
 ion_dynamics = "bfgs"
/
&CELL
 cell_dynamics = "none"
/
CELL_PARAMETERS angstrom
6.2153 0.0 0.0
0.0 8.7763 0.0
0.0 0.0 6.2347
ATOMIC_SPECIES
Ce 140.116 Ce.pbe-mt_fhi.UPF
Ba 137.327 Ba.pbe-mt_fhi.UPF
O  15.999 O.pbe-mt_fhi.UPF
ATOMIC_POSITIONS crystal
O 0.1984 0.0506 0.3043
O 0.6984 0.4494 0.1957
O 0.8016 0.5506 0.6957
O 0.3016 0.9494 0.8043
O 0.8016 0.9494 0.6957
O 0.3016 0.5506 0.8043
O 0.1984 0.4494 0.3043
O 0.6984 0.0506 0.1957
Ba 0.43716 0.25 0.01556
Ba 0.93716 0.25 0.48444
Ba 0.56284 0.75 0.98444
Ba 0.06284 0.75 0.51556
O 0.5328 0.25 0.6005
O 0.0328 0.25 0.8995
O 0.4672 0.75 0.3995
O 0.9672 0.75 0.1005
Ce 0.0 0.0 0.0
Ce 0.5 0.5 0.5
Ce 0.0 0.5 0.0
Ce 0.5 0.0 0.5
K_POINTS gamma

*Error Messages: *

1. The energy_new is clearly shown as the same as the energy_old, but it is
not what is displayed under "CASE."

[image: Inline image 1]

2. At the end of the simulation this message shows up. What does the
"maximum number of steps" referring to? I discussed with my supervisor, and
he told me that the conv_thr should not be reduced, so I couldn't use that
to solve my problem. And the final atomic coordinates are the same as my
initial coordinates.

[image: Inline image 2]
[image: Inline image 4]

If you have any suggestions on how to correct these errors, that would be
great! Thank you so much!

Best,
*Chen (Bonnie) Wang*
Department of Materials Science and Engineering
Massachusetts Institute of Technology | 2017
chenbon at mit.edu | (505) 600-5828
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