[Pw_forum] TiO2.nscf

[funmi ayedun]

Dear All, 
Good day to you all. 
When I was working on TiO2 .scf.in, I have succeded in getting convergency? for 
celldium 1 (i.e. a) and celldium 3 which is c/a. I am now on TiO2.nscf.in. The 
system is complaining about my nbnd., calculation. I am not even too sure of my 
high symmetric?? values? of my K points. Please? assist me am still fresh in 
the use of quantum espresso.


? calculation = 'nscf',
? restart_mode='from_scratch',
? prefix='TiO2'
? pseudo_dir='/home/funmilayo/espresso-4.2.1/pseudo',
? outdir='./',
??? tprnfor = .true.
? tstress = .true.
/

?ibrav=6, celldm(1)= 8.9300,celldm(3)= 0.6943, nspin =2, 
starting_magnetization(1) = 0.7,
? nat=3, ntyp=2,occupations='smearing', nbnd =16. 
smearing='marzari-vanderbilt', degauss= 0.06 
? ecutwfc= 50.0, ecutrho = 200.0
/

?mixing_beta = 0.7
?diagonalization='davidson'
conv_thr =? 1.0d-8
/
ATOMIC_SPECIES
Ti 47.867? Ti.blyp-sp-van_ak.UPF
O? 15.994? O.blyp-van_ak.UPF
ATOMIC_POSITIONS
Ti 0.?? 0.?? 0. 
O? 0.?? 0.?? 0.
O? 0.8000?? 0.2000?? 0.5000
K_POINTS 
?10
0.125? 0.125? 0.125? 1.00
0.125? 0.125? 0.375? 3.00
0.125? 0.125? 0.625? 3.00
0.125? 0.125? 0.875? 3.00
0.125? 0.375? 0.375? 3.00
0.125? 0.375? 0.625? 6.00
0.125? 0.375? 0.875? 6.00
0.125? 0.625? 0.625? 3.00
Thank you all and stay blessed.
Ayedun Funmilayo,
PhD Student,
Department of Physics,
Federal University of Agriculture,
Abeokuta,
Nigeria.


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[Pw_forum] Equation of state with PW.x

[GAO Zhe]

Dear Furman:
I think, the easier and better way to make such a "compress" is using isostatic 
pressure, which can be specified by parameter "press" in "cell" namelist, 
especially for the un-cubic system. For example, in HCP structure, the cell is 
determined by "a" and "a/c", while the volume changing, not only "a", but also 
"a/c" ratio changes, too.
Therefore, you can do a batch of "vc-relax" tasks with different press and 
gather the final volume and total energy to fit EOS. The aim compress, as 10% 
or 20% shrinkage, can be found from EOS fitting result, where you can obtain 
the P-V curve.


--
GAO Zhe
CMC Lab, Materials Science & Engineering Department,
Seoul National University, South Korea
 

At 2012-06-08 15:17:36,"David Furman"  wrote:


Hello dear users and developers,

 

I'm trying to calculate the equation of state of Europium oxide, but I have 
some doubts regarding my procedure.

I have the xyz coordinates of the unit cell in angstroms which I put into 
atom_positions and also define the needed celldm's().

 

I'm interested to compress the material to different values (say, 0%, 10% and 
20% volumetric compression) and calculate the total energy each time.

 

Do I have to change the given initial xyz coordinates in atom_positions AND the 
celldm() , or just change the celldm() accordingly to the compression and pw.x 
will do the proper changes to the positions of the atoms ?

 

I have done some calculations with uncompressed unit cell and with 20% 
compressed unit cell (by changing to the proper compressed celldm() values) but 
the difference in energy was about 0.5 Ry which i believe to be quite small. 
(Of course I checked previously for convergence).

 

Am I doing it wrong ?

 

Any help will be greatly appreciated

 

David Furman, Graduate Student| Fritz Haber Research Center for

Molecular Dynamics, The Hebrew University of Jerusalem | +972-8656-8909

 
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