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.*.