Hello everyone,
Problem 1
---------------------------------------
I'm computing for lattice constant and comparing the employment of
exchange correlation ultra-soft pp such as LDA, PBE and PBEsol. I know
LDA would underestimate the lattice parameter, PBE would overestimate it
but PBEsol should do better than PBE.
My calculations are shows LDA= 3.419 PBE= 3.516 PBEsol = 3.455 Angstom.
experimnetal value I'm comparing it to is 3.522 Ang
PBEsol gave a lower atomic lattice value than PBE.
What could be wrong with the composition of the system?
Attached is the input file(vc_ni-bulk-pbesol.in) for the PBEsol USPP
calculations.
Problem 2
-------------------------------------------
Trying to find Cohesive energy and I already have my energy of the bulk.
I'm now computing for the energy of a single atom in a vacuum system.
I added 15 15 15 Ang to the XYZ Cell parameters and the single atom sits
in a corner whiles I expect it to sit some where in the middle.
What I'm I not doing right please.
Attached is the respective (evac-ni.in) file too.
Thank you.
Kind Regards,
Elliot
--
Elliot S. Menkah
Research Student - Computational Chemistry/ Computational Material Science
Theoretical and Computational Chemistry
Dept. of Chemistry
Kwame Nkrumah UNiversity of Sci. and Tech.
Kumasi
Ghana
Tel: +233 243-055-717
Alt Email: [email protected]
[email protected]
&CONTROL
title = 'Bulk-Nickel',
calculation = 'vc-relax',
restart_mode = 'from_scratch',
wf_collect = .true.,
outdir = './temp',
wfcdir = './wftemp',
pseudo_dir = '/home/mmc14/pseudo',
prefix = 'Ni-bulk-pbe',
tstress = .true.,
tprnfor = .true.,
/
&SYSTEM
ibrav = 0,
celldm(1) = 1.889725989,
nat = 4,
ntyp = 1,
nbnd = 30,
ecutwfc = 40.0
ecutrho = 320.0,
occupations ='smearing',
smearing ='mp',
degauss =0.005D0,
nspin = 2,
starting_magnetization(1)=0.5,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0D-8,
mixing_beta = 0.2
/
&IONS
ion_dynamics = 'bfgs' ,
/
&CELL
cell_dynamics = 'bfgs' ,
/
ATOMIC_SPECIES
Ni1 58.6934 Ni.pbesol-n-kjpaw_psl.0.1.UPF
ATOMIC_POSITIONS {alat}
Ni1 1.7691699470 1.7691699470 0.0000000000
Ni1 0.0000000000 0.0000000000 0.0000000000
Ni1 1.7691699470 0.0000000000 1.7691699470
Ni1 0.0000000000 1.7691699470 1.7691699470
K_POINTS automatic
7 7 7 0 0 0
CELL_PARAMETERS
3.5383398940 0.0000000000 0.0000000000
0.0000000000 3.5383398940 0.0000000000
0.0000000000 0.0000000000 3.5383398940
&CONTROL
title = 'Bulk-Nickel',
calculation = 'vc-relax',
restart_mode = 'from_scratch',
wf_collect = .true.,
outdir = './temp',
wfcdir = './wftemp',
pseudo_dir = '/home/mmc14/pseudo',
prefix = 'Ni-bulk-pbe',
tstress = .true.,
tprnfor = .true.,
/
&SYSTEM
ibrav = 0,
celldm(1) = 1.889725989,
nat = 1,
ntyp = 1,
nbnd = 30,
ecutwfc = 40.0
ecutrho = 320.0,
occupations ='smearing',
smearing ='mp',
degauss =0.005D0,
nspin = 2,
starting_magnetization(1)=0.5,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0D-8,
mixing_beta = 0.2
/
&IONS
ion_dynamics = 'bfgs' ,
/
&CELL
cell_dynamics = 'bfgs' ,
/
ATOMIC_SPECIES
Ni1 58.6934 Ni.pbe-nd-rrkjus.UPF
ATOMIC_POSITIONS {alat}
Ni1 0.000000000 0.000000000 0.000000000
K_POINTS automatic
7 7 7 0 0 0
CELL_PARAMETERS
18.516680427 0.000000000 0.000000000
0.000000000 18.516680427 0.000000000
0.000000000 0.000000000 18.516680427
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