View source for Explanations of input files (ground state of C2H2 molecule)

== required and recommened variables ==

=== &units ===

Mandatory: none

 &units
   unit_system='A_eV_fs'
 /

This namelist specifies the unit system to be used in the input file. 
If you do not specify it, atomic unit will be used.
See [[Input variables#&units]] for detail.

For isolated systems (specified by <code>iperiodic = 0</code> in <code>&system</code>), the unit of 1/eV is used for the output files of DOS and PDOS if <code>unit_system = 'A_eV_fs'</code> is specified, while atomic unit is used if not. For other output files, the Angstrom/eV/fs units are used  irrespective of the namelist value.

=== &calculation ===

Mandatory: calc_mode

 &calculation
   calc_mode = 'GS'
 /

This indicates that the ground state (GS) calculation is carried out in the present job. See [[Tutorial-v.1.0.0#&calculation]] for detail.

=== &control ===

Mandatory: none

 &control
   sysname = 'C2H2'
 /

'C2H2' defined by <code>sysname = 'C2H2'</code> will be used in the filenames of output files.

=== &system ===

Mandatory: iperiodic, al, nstate, nelem, natom

 &system
   iperiodic = 0
   al = 16d0, 16d0, 16d0
   nstate = 5
   nelem = 2
   natom = 4
   nelec = 10
 /

<code>iperiodic = 0</code> indicates that the isolated boundary condition will be used in the calculation. 
<code>al = 16d0, 16d0, 16d0</code> specifies the lengths of three sides of the rectangular parallelepiped where the grid points are prepared. 
<code>nstate = 8</code> indicates the number of Kohn-Sham orbitals to be solved.
<code>nelec = 10</code> indicate the number of valence electrons in the system. Since the present code assumes that the system is spin saturated, <code>nstate</code> should be equal to or larger than <code>nelec/2</code>.
<code>nelem = 2</code> and <code>natom = 4</code> indicate the number of elements and the number of atoms in the system, respectively.
See [[Input variables#&system]] for more information.

=== &pseudo ===

Mandatory: pseudo_file, izatom

 &pseudo
   izatom(1)=6
   izatom(2)=1
   pseudo_file(1)='C_rps.dat'
   pseudo_file(2)='H_rps.dat'
   lmax_ps(1)=1
   lmax_ps(2)=0
   lloc_ps(1)=1
   lloc_ps(2)=0
 /

Parameters related to atomic species and pseudopotentials. 
<code>izatom(1) = 6</code> specifies the atomic number of the element #1.
<code>pseudo_file(1) = 'C_rps.dat'</code> indicates the filename of the pseudopotential of element #1. 
<code>lmax_ps(1) = 1</code> and <code>lloc_ps(1) = 1</code> specify the maximum angular momentum of the pseudopotential projector and the angular momentum of the pseudopotential that will be treated as local, respectively.

=== &rgrid ===

Mandatory: dl or num_rgrid

 &rgrid
   dl = 0.25d0, 0.25d0, 0.25d0
 /

<code>dl = 0.25d0, 0.25d0, 0.25d0</code> specifies the grid spacings in three Cartesian directions.
See [[Input variables#&rgrid]] for more information.

=== &scf ===

Mandatory: nscf

 &scf
   ncg = 4
   nscf = 1000
   convergence = 'norm_rho_dng'
   threshold_norm_rho = 1.d-15
 /

<code>ncg</code> is the number of CG iterations in solving the Khon-Sham equation. <code>nscf</code> is the number of scf iterations. For isolated systems specified by <code>&system/iperiodic = 0</code>, the scf loop in the ground state calculation ends before the number of the scf iterations reaches <code>nscf</code>, if a convergence criterion is satisfied. There are several options for the convergence check. If the value of <code>norm_rho_dng</code> is specified, the convergence is examined by the squared difference of the electron density,

=== &analysis ===

The following namelists specify whether the output files are created or not after the calculation.

 &analysis
   out_psi = 'y'
   out_dos = 'y'
   out_pdos = 'y'
   out_dns = 'y'
   out_elf = 'y'
 /

=== &atomic_coor ===

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

 &atomic_coor
 'C'    0.000000    0.000000    0.599672  1
 'H'    0.000000    0.000000    1.662257  2
 'C'    0.000000    0.000000   -0.599672  1
 'H'    0.000000    0.000000   -1.662257  2
 /

Cartesian coordinates of atoms. The first column indicates the element. Next three columns specify Cartesian coordinates of the atoms. The number in the last column labels the element.