Quantum Espresso Tutorial: h-Boron Phosphide Variable-Cell Relaxation

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SUMMARY

The discussion focuses on using Quantum Espresso for simulating hexagonal boron phosphide (h-BP) with variable-cell relaxation. The user encounters issues with atom distances being too short and incorrect Fermi levels despite multiple configuration attempts. The provided input parameters include settings for the control, system, electrons, ions, and cell sections, with specific values for ecutwfc, ecutrho, and DFT functional. The user seeks feedback on their input to ensure proper setup for the simulation.

PREREQUISITES
  • Familiarity with Quantum Espresso version 6.8 or later
  • Understanding of variable-cell relaxation techniques in computational materials science
  • Knowledge of DFT (Density Functional Theory) and PBE (Perdew-Burke-Ernzerhof) functional
  • Experience with input file structure and parameters in Quantum Espresso
NEXT STEPS
  • Review Quantum Espresso documentation on variable-cell relaxation settings
  • Learn about optimizing input parameters for DFT calculations
  • Explore troubleshooting techniques for common issues in Quantum Espresso simulations
  • Investigate the effects of different pseudopotentials on simulation outcomes
USEFUL FOR

Researchers and students in computational materials science, particularly those working with Quantum Espresso for simulating boron phosphide structures and optimizing DFT calculations.

Alessandroocj
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Hello my dear fellows, how're you doing? I'm trying to learn how to use Quantum Espresso, and in order to do this, I'm trying to simulate a hexagonal boron phosphide primary cell. At the end of the simulation, the structure seems to be fine, but sometimes the distance of the atoms are too short, and the Fermi level seems to be wrong in all my attempts to solve the problem. I've already tried many different configurations. Could someone gently check my input to see if everything is OK? =)
Here is my input for the variable-cell relaxation

!===========================================================
!
! Quantum Espresso calculation - h-Boron Phosphide
! Variable-cell relaxation
!===========================================================
&CONTROL

calculation='vc-relax'
title='h-bp'
prefix='h-bp'
verbosity='high'
restart_mode='from_scratch'
!nstep=1000
!iprint=1
outdir='./results'
pseudo_dir='./'
!tstress=.true.
forc_conv_thr=1.0d-5
etot_conv_thr=1.0d-6

/

&SYSTEM

ibrav = 0, !lattice is specified below
nat = 2,
ntyp = 2,
ecutwfc = 100.0 ,
ecutrho = 700.0 ,
input_DFT = 'PBE' ,
!occupations = 'smearing',
!degauss = 1.0d-4 ,
!smearing ='marzari-vanderbilt' ,
lspinorb=.true.
noncolin=.true.

/

&ELECTRONS

electron_maxstep = 500,
conv_thr = 1.0d-10,
mixing_mode = 'plain',
mixing_beta = 0.7d0,
diagonalization = 'cg',

/

&IONS
ion_dynamics='bfgs'
upscale=20.0

/

&CELL

! press_conv_thr = 0.5D0
! press = 0.D0
! cell_dynamics = bfgs,
! cell_dofree = '2Dxy'
cell_factor = 3.0D0

/

ATOMIC_SPECIES

B 10.810 B.rel-pbe-n-kjpaw_psl.0.1.UPF
P 30.974 P.rel-pbe-n-kjpaw_psl.1.0.0.UPF

CELL_PARAMETERS (angstrom)

2.1300000 1.2300000 0.0000000
2.1300000 -1.2300000 0.0000000
0.0000000 0.0000000 6.0000000

ATOMIC_POSITIONS (angstrom)

B 0.000000000 0.000000000 3.000000000

P 1.300000000 0.000000000 3.000000000

K_POINTS automatic

12 12 1 0 0 0
 
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