4 Using CP
Keywords: user_guide

Next: 4.1 Reaching the electronic Up: User's Guide for The Previous: 3.2 Format of arrays Contents

# 4 Using `CP`

It is important to understand that a CP simulation is a sequence of different runs, some of them used to "prepare" the initial state of the system, and other performed to collect statistics, or to modify the state of the system itself, i.e. modify the temperature or the pressure.

To prepare and run a CP simulation you should first of all define the system:

> atomic positions
> system cell
> pseudopotentials
> cut-offs
> number of electrons and bands (optional)
> FFT grids (optional)

An example of input file (Benzene Molecule):

             &control
                title = 'Benzene Molecule',
                calculation = 'cp',
                restart_mode = 'from_scratch',
                ndr = 51,
                ndw = 51,
                nstep = 100,
                iprint = 10,
                isave = 100,
                tstress = .TRUE.,
                tprnfor = .TRUE.,
                dt    = 5.0d0,
                etot_conv_thr = 1.d-9,
                ekin_conv_thr = 1.d-4,
                prefix = 'c6h6',
                pseudo_dir='/scratch/benzene/',
                outdir='/scratch/benzene/Out/'
             /
             &system
                ibrav = 14,
                celldm(1) = 16.0,
                celldm(2) = 1.0,
                celldm(3) = 0.5,
                celldm(4) = 0.0,
                celldm(5) = 0.0,
                celldm(6) = 0.0,
                nat = 12,
                ntyp = 2,
                nbnd = 15,
                ecutwfc = 40.0,
                nr1b= 10, nr2b = 10, nr3b = 10,
                input_dft = 'BLYP'
             /
             &electrons
                emass = 400.d0,
                emass_cutoff = 2.5d0,
                electron_dynamics = 'sd'
             /
             &ions
                ion_dynamics = 'none'
             /
             &cell
                cell_dynamics = 'none',
                press = 0.0d0,
              /
              ATOMIC_SPECIES
              C 12.0d0 c_blyp_gia.pp
              H 1.00d0 h.ps
              ATOMIC_POSITIONS (bohr)
              C     2.6 0.0 0.0
              C     1.3 -1.3 0.0
              C    -1.3 -1.3 0.0
              C    -2.6 0.0 0.0
              C    -1.3 1.3 0.0
              C     1.3 1.3 0.0
              H     4.4 0.0 0.0
              H     2.2 -2.2 0.0
              H    -2.2 -2.2 0.0
              H    -4.4 0.0 0.0
              H    -2.2 2.2 0.0
              H     2.2 2.2 0.0

You can find the description of the input variables in file `Doc/INPUT_CP.*`.

Subsections

- 4.1 Reaching the electronic ground state
- 4.2 Relax the system
- 4.3 CP dynamics
  - 4.3.0.1 Varying the temperature
  - 4.3.0.2 Nośe thermostat for electrons
- 4.4 Advanced usage
  - 4.4.1 Self-interaction Correction
  - 4.4.2 ensemble-DFT
  - 4.4.3 Free-energy surface calculations
  - 4.4.4 Treatment of USPPs
  - 4.4.5 Hybrid functional calculations using maximally localized Wannier functions