Defining a simple cubic unit cell  [SOLVED]

Total energy, geometry optimization, DFT+U, spin....

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raul_l
Posts: 74
Joined: Sun Jan 08, 2012 7:45 pm

Defining a simple cubic unit cell

Post by raul_l » Wed Sep 09, 2015 2:40 pm

Interestingly, I'm having difficulty understanding how to write input for a simple cubic cell. When I do structural optimization for CsI I get a lattice constant of 6.0 bohr, which, taking into account the slight underestimation of LDA, is sqrt(2) times smaller than the experimental value of 8.629 (4.566 A). Is it possible that a factor of sqrt(2) is related to conversion from the conventional to the primitive cell? I thought for a simple cubic cell these were the same.

Code: Select all

# CsI, HGH PPs taken from Abinit website

ndtset 7

acell1   3*5.7
acell1   3*5.8
acell2   3*5.9
acell3   3*6.0
acell4   3*6.1
acell5  3*6.2
acell6  3*6.3
acell7  3*6.4
rprim
  1 0 0
  0 1 0
  0 0 1
ntypat   2
znucl    55 53
natom    2
typat    1 2
xred     3*0.0 3*0.5

ngkpt    3*8
shiftk   3*0.0
nband    6
nbdbuf   2

ecut     60

tolvrs   1d-9

diemac   5.6
Last edited by raul_l on Wed Sep 09, 2015 6:04 pm, edited 1 time in total.
Raul Laasner
Netherlands Institute for Space Research

raul_l
Posts: 74
Joined: Sun Jan 08, 2012 7:45 pm

Re: Defining a simple cubic unit cell  [SOLVED]

Post by raul_l » Wed Sep 09, 2015 6:03 pm

Never mind. I was using the wrong pseudopotential.
Notice for others: when downloading an HGH PP from the Abinit website, the blue and green areas are actually different links. Be careful where you click!
Raul Laasner
Netherlands Institute for Space Research

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