[Pw_forum] cohesive energy

[lan haiping]

Hi,
A comment:
Spin polarization calculation should be applied for the isolated atom.

Hope it helps, and please supply your affiliation

regards
On Tue, Sep 1, 2009 at 2:18 AM, udayagiri sai babu <udayagiri3 at gmail.com>wrote:

> Hi all
> i am claculating cohesive energy of V using pwscf but i got -8.15 ev/atom
> against an experimental value of 5.3 ev/atom which is almost 50% off can
> anybody say what is going wrong with the calculation. the method i used is
> calculate the total energy of a bcc crystal with 1 atom and deduct the
> energy of isolated atom from it. the following input files are for finding
> the total energy for isolated atom and the atom in the crystal. Please tell
> me if my methodology is wrong.
>
> *cohesive energy=E per atom (in the crystal)-E per atom (isolated)*
>
> *input file for finding the total energy of an isolated atom*
>
> &control
> calculation = 'scf',
> restart_mode='from_scratch',
> outdir='/home/sai/temp',
> prefix='vanadium'
> pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',
> tstress = .TRUE.,
> tprnfor = .TRUE.,
> /
> &system
> ibrav=1
> celldm(1)=30,
> nat=1,
> ntyp=1
> ecutwfc=25,
> ecutrho=100,
> occupations='smearing',
> smearing='mv',
> degauss=0.010000
> /
> &electrons
> conv_thr=1.D-8,
> diagonalization='david',
>   mixing_mode='plain',
> mixing_beta= 0.3
> /
> ATOMIC_SPECIES
> V  50.9415  V.pbe-n-van.UPF
> ATOMIC_POSITIONS (crystal)
> V       0.00000000      0.00000000      0.00000000
> K_POINTS {automatic}
> 1 1 1 0 0 0
>
> *input file for finding the total energy of the atom in the crystal*
>
> &control
> calculation = 'scf',
> restart_mode='from_scratch',
> outdir='/home/sai/temp',
> prefix='vanadium'
> pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',
> tstress = .TRUE.,
> tprnfor = .TRUE.,
> /
> &system
> ibrav=3
> celldm(1)=5.654,
> nat=1,
> ntyp=1
> ecutwfc=25,
> ecutrho=100,
> occupations='smearing',
> smearing='mv',
> degauss=0.010000
> /
> &electrons
> conv_thr=1.D-8,
> diagonalization='david',
> mixing_mode='plain',
> mixing_beta= 0.3
> /
> ATOMIC_SPECIES
> V  50.9415  V.pbe-n-van.UPF
> ATOMIC_POSITIONS (crystal)
> V       0.00000000      0.00000000      0.00000000
> K_POINTS {automatic}
> 8 8 8 0 0 0
>
>
>
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>


-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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