Section &CPMD ...&END

It is compulsory to put one of the following keywords.
MOLECULAR DYNAMICS, OPTIMIZE {GEOMETRY,WAVEFUNCTION} are mutually exclusive.

MOLECULAR DYNAMICS

Perform a molecular dynamics run.

OPTIMIZE {GEOMETRY,WAVEFUNCTION,COMBINED}

Causes the program to optimize either the geometry and the wavefunction of the system (GEOMETRY) or the wavefunction only (WAVEFUNCTION). COMBINED stands for a molecular dynamics based geometry optimization method. This method is not yet fully operational in the current version.

KOHN-SHAM ENERGIES [OFF]

Calculate the Kohn-Sham energies and the corresponding orbitals. The number of states in addition to the occupied states that have to be calculated is read from the next line. The Kohn-Sham orbitals are stored on the file RESTART.x. Default is not to calculate Kohn-Sham energies.
Warning: The usage of this keyword needs special care (especially restarts).

VIBRATIONAL ANALYSIS

Calculate harmonic frequencies by finite differences of first derivatives.

PROPERTIES

Calculate some properties. This keyword requires further input in the section &PROP ... &END.

Further keywords

PARRINELLO-RAHMAN {NPT}

To be used together with Molecular Dynamics. A variable cell MD with the Parrinello-Rahman Lagrangian is performed. With the additional keyword a constant NPT MD using the method of Martyna, Tobias, and Klein[] is used.
If this keyword is used together with other run options like OPTIMIZE WAVEFUNCTIONS, calculations with different reference cells can be performed.

LSD

Use the local spin density approximation. Not all functionals are implemented for this option.

MAXSTEP

The maximum number of steps to be performed is read from the next line. Default is 10000 steps.

TIMESTEP

The time step in atomic units is read from the next line. Default is a timestep of 5 a.u.
1 a.u. = 0.0241888428 fs

EMASS

The fictitious electon mass in atomic units is read from the next line. Default is 400 a.u.

RESTART [Options]

Read the quantites specified with option from
restart files.
List of valid options :

WAVEFUNCTION

Read old wavefunction from restart file.

COORDINATES

Read old coordinates from restart file.

VELOCITIES

Read old ionic, wavefunction and cell velocities from restart file.

CELL

Read old cell parameters from restart file.

GEOFILE

Read old ionic positions and velocities from file GEOMETRY. This file is updated every timestep.

ACCUMULATORS

Read old accumulator values from restart file.

HESSIAN

Read old approximate Hessian from file HESSIAN.

NOSEE

Restart Nosé thermostats for electrons with values stored on restart file.

NOSEP

Restart Nosé thermostats for ions with values stored on
restart file.

NOSEC

Restart Nosé thermostats for cell parameters with values stored on restart file.

LATEST

Restart from the latest restart file as indicated in file LATEST.

VIBANALYSIS

Use the information on finite differences stored in the file FINDIF. This option requires a valid restart file for the wavefunctions, even when wavefunctions and coordinates are recalculated or read from the input file.

POTENTIAL

Read an old potential from the restart file. This applies to restarts for Kohn-Sham energy calculations.

NONORTHOGONAL ORBITALS [OFF]

Use the norm constraint
method [5] for molecular dynamics or nonothogonal orbitals in an optimization run. On the next line the limit of the off diagonal elements of the overlap matrix is defined. Warning: Adding or deleting this option during a MD run needs special care.

HARMONIC REFERENCE SYSTEM [OFF]

Switches harmonic reference system integration on/off. The number of shells included in the analytic integration is controled with the keyword HAMILTONIAN CUTOFF. By default this option is switched off.

SCALED MASSES [OFF]

Switches the usage of g-vector dependent
masses on/off. The number of shells included in the analytic integration is controled with the keyword HAMILTONIAN CUTOFF. By default this option is switched off.

STEEPEST DESCENT [ELECTRONS,IONS,NOPRECONDITIONING]

Use the method of steepest descent for the optimization of wavefunction and/or atomic positions. If both options are specified in a geometry optimization run, a simultaneous optimization is performed. Preconditioning of electron masses (scaled masses) is used by default. The preconditioning is controled by the keyword HAMILTONIAN CUTOFF. Optionally preconditioning can be disabled.

ODIIS [NOPRECONDITIONING]

Use the method of direct inversion in the iterative subspace for optimization of the wavefunction. [6] The number of DIIS vectors is read from the next line. ODIIS with 10 vectors is the default method in optimization runs. The preconditioning is controled by the keyword HAMILTONIAN CUTOFF. Optionally preconditioning can be disabled.

PCG [MINIMIZE,NOPRECONDITIONING]

Use the method of preconditioned conjugate gradients for optimization of the wavefunction. If option MINIMIZE is not chosen then no line searches are performed. The fixed steplength is controlled by the keywords
TIMESTEP and EMASS. The preconditioning is controled by the keyword HAMILTONIAN CUTOFF. Optionally preconditioning can be disabled.

GDIIS

Use the method of direct inversion in the iterative subspace combined with a quasi-Newton method (using BFGS) for optimization of the ionic positions [12, ]. The number of DIIS vectors is read from the next line. GDIIS with 5 vectors is the default method in optimization runs.

BFGS

Use a quasi-Newton method for optimization of the ionic positions. The approximated Hessian is updated using the Broyden-Fletcher-
Goldfarb-Shano procedure. [13]

RFO ORDER=nsorder

Rational function approximation combined with a quasi-Newton method (using BFGS) for optimization of the ionic positions is used.[7] A saddle point of order nsorder is searched for.

INITIALIZE WAVEFUNCTION {RANDOM,ATOMS}

The initial guess for wavefunction optimization are either random functions or functions derived from the atomic pseudo-wavefunctions. Default is to use the atomic pseudo-wavefunctions.

HAMILTONIAN CUTOFF

The lower cutoff for the diagonal approximation to the Kohn-Sham matrix is read from the next line. Default is 0.5 atomic units. For variable cell dynamics only the kinetic energy as calculated for the reference cell is used.

ORTHOGONALIZATION {LOWDIN,GRAM-SCHMIDT}

Orthogonalization in optimization runs is done either by a Lowdin (symmetric) or Gram-Schmidt procedure. Default is Gram-Schmidt except for parallel runs where Lowdin orthogonalization is used.

RATTLE

This option can be used to set the maximum number of iterations and the tolerance for the iterative orthogonalization. These two numbers are read from the next line. Defaults are 30 and .

QUENCH [IONS,ELECTRONS,BO]

The velocities of the ions or wavefunctions are set to zero at the begining of a run. With the option BO the wavefunctions are converged at the beginning of the MD run.

DAVIDSON

This keyword controls the Davidson diagonalisation routine used to determine the Kohn-Sham energies. The maximum number of additional vectors to construct the Davidson matrix and the convergence criterion are read from the next line. Defaults are and the same number as states to be optimized. If the system has 20 occupied states and you ask for 5 unoccupied states, the default number of additional vectors is 25. By using less than 25 some memory can be saved but convergence might be somewhat slower.

DUAL

The ratio between the plane wave cutoff for the density and the wavefunction is read from the next line. The default is 4.

RANDOMIZE {COORDINATES,WAVEFUNCTION,CELL}

The ionic positions or the wavefunction or the cell parameters are randomly displaced at the begining of a run. The maximal amplitude of the displacement is read from the next line.

TEMPERATURE

The initial temperature in Kelvin of the system is read from the next line.

TEMPCONTROL {IONS,ELECTRONS}

The temperature of the
ions in Kelvin or the fictitious kinetic energy of the electrons in atomic units is controlled by scaling. The target temperature and the tolerance for the ions or the target kinetic energy and the tolerance are read from the next line.

NOSE {IONS,ELECTRONS,CELL} [ULTRA,MASSIVE]

Nosé-Hoover chains [8, 9] for the ions, electrons, and/or cell parameters are used. The target temperature in Kelvin and the thermostat frequency in , respectively the fictitious kinetic energy in atomic units and the thermostat frequency in are read from the next line. For the ionic case the additional keyword ULTRA selects a thermostat for each species, and the keyword MASSIVE selects a thermostat for each degree of freedom.

NOSE PARAMETERS

The parameters controlling the Nosé thermostats are read in the following order from the next line. The length of the Nosé-Hoover chain for the ions (default is 4), the length of the Nosé-Hoover chain for the electrons (default is 4), the length of the Nosé-Hoover chain for the cell parameters (default is 4), the scaling factor for the number of electronic degrees of freedom (default is 1), the order of the Suzuki/Yoshida integrator (default is 15, the maximum 625), and the decomposition ratio of the time step (default is 1). If this keyword is ommitted, the defaults are used. If the keyword is used all parameters have to be specified.

PRINT [INFO,COORDINATES,FORCES]

A detailed output is
printed every IPRINT iterations. Either only different contribution to the energy or in addition the atomic coordinates and the forces are printed. IPRINT is read from the next line. Default is only the energies after the first step and at the end of the run.

STORE

The restart file is updated every ISTORE steps. ISTORE is read from the next line. Default is at the end of the run.

CONVERGENCE

The convergence criteria for optimization runs is specified. The maximum value for the biggest element of the gradient of the wavefunction and of the ions is read from the next line. Default values are for the wavefunction and for the ions.

DIPOLE DYNAMICS [SAMPLE]

Calculate the dipole moment every NSTEP iteration in MD. NSTEP is read from the next line if the keyword SAMPLE is present. Default is every time step.

STRESS TENSOR

Calculate the stress tensor every NSTEP iteration in a constant volume MD. NSTEP is read from the next line.

ANNEALING

Scale the ionic velocities every time step. The scaling factor is read from the next line.

HESSIAN {DISCO,SCHLEGEL,UNIT}

The initial approximate Hessian for a geometry optimization is constructed using empirical rules with the DISCO [11] or Schlegel's [10] parametrization or simply a unit matrix is used.

FINITE DIFFERENCES

The step length in a finite difference run for vibrational frequencies is read from the next line.

PROJECT {NONE,DIAGONAL,FULL}

This keyword is controling
the calculation of the constraint force in optimization runs.

STRUCTURE [BONDS, ANGLES, DIHEDRALS]

Print structure information at the end of the run. Dihedral angles are defined between 0 and 180 degrees. This might change in the future.

RHOOUT [BANDS]

Store the density at the end of the run on file DENSITY. If the keyword BANDS is defined then on the following lines the number of bands to be plotted and their position has to be given. If the position specification is a negative number, then the wavefunction not the density is written. Each band is stored on its own file DENSITY.num. For spin polarized calculations besides the total density also the spin density is stored on the file SPINDEN.

RESTFILE

The number of distinct restart files is read from the next line. The restart files are written in turn. Default is 1. If you specify e.g. 3, then the files RESTART.1, RESTART.2, RESTART.3 are used.

TRAJECTORY [OFF, SAMPLE]

Store the atomic positions and velocities at every NTRAJ time step on file TRAJECTORY. This is the default for MD runs. If the keyword SAMPLE is given NTRAJ is read from the next line, the default value for NTRAJ is 1.

MOVIE [OFF]

Write the atomic coordinates without applying periodic boundary conditions in MOVIE [14] format every IMOVIE time steps on file MOVIE. IMOVIE is read from the next line. Default is not to write a movie file.

BIG MEMORY

The structure factors for the density cutoff are only calculated once and stored for reuse. Default is to recalculate them whenever needed. This option allows for considerable time savings in connection with Vanderbilt pseudopotentials.

COMPRESS [WRITEnn]

Write the wavefunctions with nn bytes precision to the restart file. Possible choices are WRITE32, WRITE16, WRITE8, WRITEAO. WRITE32 corresponds to the compress optimon in older versions. WRITEAO stores the wavefunction as a projection on atomic basis sets. Tha atomic basis set can be specified in the section &BASIS ...&END. If this input section is missing a default basis from Slater type orbitals is constructed.

ISOLATED MOLECULE

Treat the system as an isolated molecule. This affects the calculation of the number of degrees of freedom.

CENTER MOLECULE [OFF]

The center of mass is moved/not moved to the center of the computational box in a calculation with the cluster option. This is only done when the coordinates are read from the input file.

COULOMB SMOOTHING

The smoothing radius of the Coulomb interaction is read from the next line. This only applies to calculations on isolated systems.

SPLINE [POINTS,QFUNCTION]

This option controls the generation of the pseudopotential functions in g-space. All pseudopotential functions are first initialized on a evenly spaced grid in g-space and then calculated at the needed positions with a spline interpolation. The number of spline points is read from the next line when POINTS is specified. The default number is 251. In addition it is possible to keep the Q-functions of the Vanderbilt pseudopotentials on the spline grid during the whole calculation and do the interpolation whenever needed. This option may be useful to save time during the initialization phase and memory in the case of Vanderbilt pseudopotentials when the number of shells is not much smaller than the total number of planewaves, i.e. for all cell symmetries except simple cubic and fcc.

BENCHMARK

This keyword is used to control some special features related to benchmarks. If you want to know more, have a look in the source code.

REAL SPACE WFN [KEEP]

The number of wavefunctions that are Fourier transformed at the same time is read from the next line. This allows for larger message sizes in parallel runs. With the option KEEP one asks for storing the real space wavefunctions.

FILEPATH

The path to the restart files is read from the next line. Default is the current directory.

TASKGROUPS [MINIMAL,MAXIMAL]

The number of taskgroups is read from the next line. The number of taskgroups has to be a divisor of the number of nodes in a parallel run.

CHECK MEMORY

Check sanity of dynamically allocated arrays whenever a change in the allocation is done. By default memory is checked only at break points.