QuantumESPRESSO input (pwscf)

QuantumESPRESSO is a suite of programs for electronic structure calculations based on density-functional theory (DFT). The input file for QuantumESPRESSO, commonly named input.in, is crucial for specifying the details of the simulation, including system information, calculation parameters, and method settings. Below is a simplified example of a QuantumESPRESSO input file for a molecular structure:

&CONTROL
calculation = 'scf'
restart_mode = 'from_scratch'
pseudo_dir = '/path/to/pseudopotentials/'
outdir = './tmp'
prefix = 'molecule'
disk_io = 'low'
verbosity = 'high'
/

&SYSTEM
ibrav = 1
celldm(1) = 10.0
nat = 3
ntyp = 2
ecutwfc = 30.0
occupations = 'smearing'
smearing = 'mv'
degauss = 0.02
/

&ELECTRONS
conv_thr = 1.0e-8
mixing_beta = 0.7
/

ATOMIC_SPECIES
O 16.00  O.pbe-mt_fhi.UPF
H 1.008  H.pbe-mt_fhi.UPF

ATOMIC_POSITIONS crystal
O 0.0000 0.0000 0.0000
H 0.7570 0.5860 0.0000
H -0.7570 0.5860 0.0000

K_POINTS automatic
4 4 4 0 0 0

In this example:

  • The &CONTROL block specifies global control parameters, such as the type of calculation (‘scf’ for self-consistent field), file I/O settings, and verbosity.

  • The &SYSTEM block contains information about the crystal structure (ibrav, celldm), the number of atoms and types, energy cutoff for wavefunctions (ecutwfc), and parameters related to electronic occupations and smearing.

  • The &ELECTRONS block sets convergence criteria for the electronic self-consistency loop.

  • The ATOMIC_SPECIES block defines the atomic species, masses, and pseudopotential files.

  • The ATOMIC_POSITIONS block specifies the atomic positions.

  • The K_POINTS block determines the k-point sampling scheme.

This input file is for a self-consistent field (SCF) calculation of a simple molecular structure with oxygen and hydrogen atoms. Note that the specific details, such as pseudopotential files and k-point sampling, depend on the system being studied and the desired level of accuracy. Always refer to the QuantumESPRESSO documentation for accurate and up-to-date information regarding input file parameters.