====== Crystal Structure Optimization (only relax atomic position) ======

RELAXATION calculation for Si, only relax atomic postion

===== Input files =====

atom.config

<code bash>
     2
 LATTICE
      0.00000000     2.73899206     2.73899206
      2.73899206     0.00000000     2.73899206
      2.73899206     2.73899206     0.00000000
 POSITION
  14     0.00000000     0.00000000     0.00000000 0 0 0 #Zatom x1 x2 x3 imv1 imv2 imv3
  14     0.25000000     0.23000000     0.25000000 1 1 1
</code>

<WRAP round info>   

  - atom.config file describles the cell box, atomic postitions, etc.
  - 2 atoms per unit cell.
  - LATTICE: the header of the lattice vector.
  - POSITION: the header of the atomic positions.
  - Zatom: the atomic number of this atom.
  - x1, x2, x3 are the fractional coordinate of this atom
  - imv1, imv2, imv3 indicate whether this atom will move in x, y, z directions, 1 means move; 0 means not move.

</WRAP>

===== etot.input =====

<code bash>
   1 4
   JOB = RELAX
   IN.PSP1 = Si.SG15.PBE.UPF
   IN.ATOM = atom.config
   RELAX_DETAIL = 1 100 0.005 #IMTH, NSTEP, FORCE_TOL
   ECUT = 50
   ECUT2= 200
   MP_N123 = 9 9 9 0 0 0
</code>

  - The product of the two integers on the first line must equal to the number of GPU to run PWmat.
  - ECUT is the plane wave cutoff energy of wavefunction (in //Ryd//, note: 1 //Ryd// = 13.6057 //eV//)
  - MP_N123 is the Monkhorst-Pack grids to generate the reduced k-points, so no additional k-points file is required.
  - RELAX_DETAIL: controls the atomic relaxation details.
  - IMTH: the method of relaxtion, 1: conjugated gradient.
  - NSTEP: the maximum number of relaxation stpes.
  - FORCE_TOL: the force tolenrance for the maximal redidual force (eV/A).


Si.SG15.PBE.UPF

Si.SG15.PEB.UPF is the pseudopotential file.


===== Calculations =====

  - You can submit PWmat tasks in different ways:

<code bash>
   mpirun -np 4 PWmat | tee output
</code>

<wrap round notice> Run the command directly </wrap>

<code bash>
   #!/bin/bash
   #PBS -N SCF
   #PBS -l nodes=1:ppn=4
   #PBS -q batch
   #PBS -l walltime=100:00:00

   ulimit -s unlimited
   cd $PBS_O_WORKDIR

   mpirun -np 4 PWmat | tee output
</code>

<wrap round notice> Submit the task with a pbs script </wrap>

  - For RELAXATION calculation, files to watch during relaxations.

> RELAXSTEPS: concisely reports about the atomic relaxation steps. A typical RELAXSTEPS file looks like:

<code bash>
   It=   -1 CORR E=  -0.2144796997311E+03  Av_F=  0.58E+00 M_F=  0.71E+00 dE=  0.42E-05 dRho=  0.83E-04 SCF=    13 dL=  0.00E+00 p*F=  0.00E+00 p*F0=  0.00E+00 Fch=  0.00E+00
   It=    0  NEW E=  -0.2145128948737E+03  Av_F=  0.22E+00 M_F=  0.26E+00 dE=  0.20E-05 dRho=  0.30E-04 SCF=     6 dL=  0.92E-01 p*F= -0.37E+00 p*F0= -0.10E+01 Fch=  0.10E+01
   It=    1 CORR E=  -0.2145181062288E+03  Av_F=  0.57E-01 M_F=  0.98E-01 dE=  0.88E-06 dRho=  0.13E-04 SCF=     5 dL=  0.15E+00 p*F=  0.52E-03 p*F0= -0.10E+01 Fch=  0.99E+00
   It=    2  NEW E=  -0.2145184522502E+03  Av_F=  0.18E-01 M_F=  0.31E-01 dE=  0.59E-05 dRho=  0.32E-04 SCF=     4 dL=  0.10E-01 p*F= -0.30E-01 p*F0= -0.98E-01 Fch=  0.10E+01
   ...
   It=    7  NEW E=  -0.2145184866505E+03  Av_F=  0.14E-02 M_F=  0.17E-02 dE=  0.24E-05 dRho=  0.16E-04 SCF=     2 dL= -0.10E-02 p*F= -0.25E-02 p*F0= -0.94E-02 Fch= -0.22E+01
   It=    8 *END E=  -0.2145184866505E+03  Av_F=  0.14E-02 M_F=  0.17E-02 dE=  0.24E-05 dRho=  0.16E-04 SCF=     2 dL= -0.10E-02 p*F= -0.25E-02 p*F0= -0.94E-02 Fch= -0.22E+01
</code>

> REPORT: more detailed information about every electronic and ionic step

  - Other important files.

> final.config: holds the structure of the last ionic step, the structural result (also very important for restarting a relaxation)

> MOVEMENT: holds the structures of every ionic step during relaxations.