[Pw_forum] input file for isolated atom

[Prasenjit Ghosh]

Dear Udayagiri,

First of all it's not clear whether you have any question other than whether
your input file is correct.

Now some comments about your input file:

(a) while doing calculations for any zero dimensions you should always set
nosym =.true.
(b) Your value of degauss is too high.....you should use some value around
0.001 Ry. According to my experience, doing cal. for a single atom is
tricky, specially when you are using a smearing. Even that doesn't confirm
you will get the correct ground state for the atom. So what you should do is
at the end of the calculation check the values of the total magnetization,
absolute magnetization and the smearing contribution. The last term should
be exactly zero.
(c) You don't need to set tstress and tprnfor true.
(c) mixing_beta= 0.7 too large.....I would put something smaller....0.3
(d) I hope you have checked the convergence of ecut rho & ecutwfc.

Prasenjit.

2009/9/11 udayagiri sai babu <udayagiri3 at gmail.com>

> Hi everybody
> I want to calculate the cohesive energy of Titanium for that i need to
> calculate the energy of an isolated atom previously in the forum somebody
> has suggested me to do spin polarisation calculation for the isolated atom.
> I have written an input file accordingly some one can see and tell me if my
> input script is true. I have read the forum archives on this topic but they
> are not exactly answering my question. Can somebody please help me.
> *
> Input file for isolated atom *
>
> &control
> calculation = 'scf',
> restart_mode='from_scratch',
> outdir='/home/sai/temp',
> prefix='titanium'
> pseudo_dir='/home/sai/softwares/espresso-4.0.1/pseudo/',
> tstress = .TRUE.,
> tprnfor = .TRUE.,
> /
> &system
> ibrav=1
> celldm(1)=20,
> nat=1,
> ntyp=1
> ecutwfc=25,
> ecutrho=250,
> occupations='smearing',
> smearing='mv',
> degauss=0.010000
> nspin=2
> starting_magnetization(1)=0.2
> /
> &electrons
> conv_thr=1.D-8,
> diagonalization='david',
> mixing_mode='plain',
> mixing_beta= 0.7,
> /
> ATOMIC_SPECIES
> Ti  47.867  Ti.pbe-sp-van_ak.UPF
> ATOMIC_POSITIONS (crystal)
> Ti     0.00000000    0.00000000    0.00000000
> K_POINTS GAMMA
>
> --
> U.Saibabu
> PhD student,
> Deformation mechanisms modeling group,
> Materials engineering department,
> IISc Bangalore,
> India.
>
>
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>


-- 
PRASENJIT GHOSH,
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