[Pw_forum] about total charge and negative charge density
Silviu Zilberman
silviu at Princeton.EDU
Tue Jan 11 06:26:19 CET 2005
Hi,
I am doing an SCF calculation for a charged molecular system in vacuum.
It is a spin unrestricted system with a total spin 1/2, and charge of
-2. The system has 135 electrons.
When the SCF calculation starts it prints correctly
nelec=135.00
but the initial wavefunction integrates to
starting charge = 132.99857
which is as if the system is not charged. I am note sure why it happens
and if I should worry about it.
A second problem is that I have a relatively high percentage of grid
points with a negative charge density:
Initial potential from superposition of free atoms
npt with |zeta| > 1: 571576, npt tot 2985984, 19.14 %
npt with rhoup < 0: 810487, npt tot 2985984, 27.14 %
npt with rhodw < 0: 749915, npt tot 2985984, 25.11 %
I know that the problem is associated with representing the augmented
charge in the ultra-soft PP, but raising the energy cutoff from 180 to
300 Ryd seems to have no significant impact. I believe that it only
means that the vacuum area around my system has some small charge
oscillations that are probably not very important, but I am not
completely sure. How does PWSCF deals with negative charge density? Is
it set to zero or some small positive number? I couldn't find in the
output file the value of the total negative charge density, to verify if
it's small.
Below is my input file, and I'll greatly appreciate any comments.
Thanks, Silviu.
-------------------------------------------------------------------------------------------------------------------------------------
&control
calculation='scf'
pseudo_dir = '/home/silviu/Work/Pot/',
outdir='/home/silviu/tmp/DTN_CO_hbond/'
title='Test DTN_CO_hbond gamma only'
prefix='DTN_CO_hbond'
tprnfor=.true.,
etot_conv_thr=1e-8,
forc_conv_thr=1e-6
/
&system
ibrav=1, celldm(1) =25.0, nat=29, ntyp= 6, nbnd=68,
ecutwfc=30.0, nelec=135, ecutrho=300.0,
nspin=2, nelup=68, neldw=67, occupations = 'from_input',
starting_magnetization(1)=1.0,
starting_magnetization(2)=0.0,
starting_magnetization(3)=0.0,
starting_magnetization(4)=0.0,
starting_magnetization(5)=0.0,
starting_magnetization(6)=0.0
/
&electrons
diagonalization='davidson',
mixing_mode='plain',
mixing_beta = 0.7,
conv_thr = 1.0d-8
/
ATOMIC_SPECIES
Fe 55.845 fe_PBE.van
S 31.97207070 016-S-gpbe--bm.van
O 15.9994 008-O-gpbe--bm.van
N 14.003074002 007-N-gpbe--bm.van
C 12.0107 006-C-gpbe--bm.van
H 1.0079 001-H-gpbe--bm.van
ATOMIC_POSITIONS {bohr}
Fe 0.85720064E+01 0.11652506E+02 0.12440106E+02
Fe 0.13580956E+02 0.10724365E+02 0.12776464E+02
S 0.11304998E+02 0.13262380E+02 0.15575250E+02
S 0.11532918E+02 0.13073796E+02 0.95542313E+01
S 0.17218271E+02 0.13470868E+02 0.12643983E+02
O 0.15784826E+02 0.79419992E+01 0.16960659E+02
O 0.58108997E+01 0.87424294E+01 0.86775991E+01
O 0.47305178E+01 0.15628119E+02 0.12189682E+02
O 0.10526325E+02 0.61433920E+01 0.12765676E+02
N 0.10943016E+02 0.17636183E+02 0.12431572E+02
N 0.16106110E+02 0.75557380E+01 0.86134922E+01
N 0.54538515E+01 0.92365466E+01 0.16722747E+02
C 0.12029425E+02 0.16521024E+02 0.10191009E+02
C 0.11891356E+02 0.16656483E+02 0.14795836E+02
C 0.15159513E+02 0.87937034E+01 0.10206898E+02
C 0.14947951E+02 0.90915554E+01 0.15258577E+02
C 0.69920627E+01 0.98707589E+01 0.10173031E+02
C 0.67098909E+01 0.10109927E+02 0.15104887E+02
C 0.19986851E+02 0.11413751E+02 0.12591169E+02
C 0.11092972E+02 0.83137246E+01 0.12696193E+02
C 0.63917900E+01 0.14151226E+02 0.12332573E+02
H 0.13960616E+02 0.16898237E+02 0.14860898E+02
H 0.11024086E+02 0.17719845E+02 0.16358428E+02
H 0.90163437E+01 0.17500478E+02 0.12380238E+02
H 0.14100285E+02 0.16755378E+02 0.10240702E+02
H 0.11267336E+02 0.17493751E+02 0.85188871E+01
H 0.21656485E+02 0.12570615E+02 0.12147971E+02
H 0.20295051E+02 0.10501624E+02 0.14434828E+02
H 0.19765371E+02 0.99495688E+01 0.11135089E+02
K_POINTS
1
0.0 0.0 0.0 1.0
OCCUPATIONS
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.0
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