Explanation of input files (crystalline silicon under a pulsed electric field)

&calculation

Mandatory: calc_mode

&calculation
  calc_mode = 'GS_RT'
/

This indicates that the ground state (GS) and the real time (RT) calculations are carried out sequentially in the present job. See Input variables#&calculation for detail.

&control

Mandatory: none

&control
  sysname = 'Si'
/

'Si' defined by sysname = 'C2H2' will be used in the filenames of output files.

&system

Mandatory: periodic, al, state, nelem, natom

&system
  iperiodic = 3
  al = 10.26d0,10.26d0,10.26d0
  nstate = 32
  nelec = 32
  nelem = 1
  natom = 8
/

iperiodic = 3 indicates that three dimensional periodic boundary condition (bulk crystal) is assumed. al = 10.26d0, 10.26d0, 10.26d0 specifies the lattice constans of the unit cell. nstate = 32 indicates the number of Kohn-Sham orbitals to be solved. nelec = 32 indicate the number of valence electrons in the system. nelem = 1 and natom = 8 indicate the number of elements and the number of atoms in the system, respectively. See Input variables#&system for more information.

&pseudo

&pseudo
  izatom(1)=14
  pseudo_file(1) = './Si_rps.dat'
  lloc_ps(1)=2
/

izatom(1) = 14 indicates the atomic number of the element #1. pseudo_file(1) = 'Si_rps.dat' indicates the pseudopotential filename of element #1. lloc_ps(1) = 2 indicate the angular momentum of the pseudopotential that will be treated as local.

&functional

&functional
  xc = 'PZ'
/

This indicates that the adiabatic local density approximation with the Perdew-Zunger functional is used. We note that meta-GGA functionals that reasonably reproduce the band gap of various insulators may also be used in the calculation of periodic systems. See Input variables#&functional for detail.

&rgrid

Mandatory: dl or num_rgrid

&rgrid
  num_rgrid = 12,12,12
/

num_rgrid=12,12,12 specifies the number of the grids for each Cartesian direction. See Input variables#&rgrid for more information.

&kgrid

Mandatory: none

This namelist provides grid spacing of k-space for periodic systems.

&kgrid
  num_kgrid = 4,4,4
/

&tgrid

&tgrid
 nt=3000
 dt=0.16  
/

dt=0.16 specifies the time step of the time evolution calculation. nt=3000 specifies the number of time steps in the calculation.

&propagation

&propagation
  propagator='etrs'
/

propagator = 'etrs' indicates the use of enforced time-reversal symmetry propagator. See Input variables#&propagation for more information.

&scf

Mandatory: nscf

This namelists specify parameters related to the self-consistent field calculation.

&scf
  ncg = 5
  nscf = 120
/

ncg = 5 is the number of conjugate-gradient iterations in solving the Kohn-Sham equation. Usually this value should be 4 or 5. nscf = 120 is the number of scf iterations.

&emfield

&emfield
  trans_longi = 'tr'
  ae_shape1 = 'Acos2'
  rlaser_int_wcm2_1 = 1d14
  pulse_tw1 = 441.195136248d0
  omega1 = 0.05696145187d0
  epdir_re1 = 0.,0.,1.
/

This namelist specifies the pulsed electric field applied to the system

ae_shape1 = 'Acos2' specifies the envelope of the pulsed electric field, cos^2 envelope for the vector potential.

epdir_re1 = 0.,0.,1. specify the real part of the unit polarization vector of the pulsed electric field. Specifying only the real part, it describes a linearly polarized pulse.

laser_int_wcm2_1 = 1d14 specifies the maximum intensity of the applied electric field in unit of W/cm^2.

omega1=0.05696145187d0 specifies the average photon energy (frequency multiplied with hbar).

pulse_tw1=441.195136248d0 specifies the pulse duration. Note that it is not the FWHM but a full duration of the cos^2 envelope.

trans_longi = 'tr' specifies the treatment of the polarization in the time evolution calculation, 'tr' indicating transverse.

See Input variables#&emfield for detail.

&atomic_red_coor

Mandatory: atomic_coor or atomic_red_coor (they may be provided as a separate file)

&atomic_red_coor
 'Si'    .0      .0      .0      1
 'Si'    .25    .25    .25    1
 'Si'    .5      .0      .5      1
 'Si'    .0      .5      .5      1
 'Si'    .5      .5      .0      1
 'Si'    .75    .25   .75     1
 'Si'    .25    .75   .75     1
 'Si'    .75    .75   .25     1
/

Cartesian coordinates of atoms are specified in a reduced coordinate system. First column indicates the element, next three columns specify reduced Cartesian coordinates of the atoms, and the last column labels the element.