41.1 Options

The following options are available:

ANALYTICAL

Use analytical second derivatives of the energy. At present, analytical second derivatives are only possible for closed shell Hartree-Fock (HF) and MCSCF wavefunctions without symmetry. It is not yet possible to calculate IR-intensities analytically. Note that, due to technical reasons, the analytical MCSCF second derivatives have to be computed in the MCSCF-program using e.g. multi; cpmcscf,hess (see MULTI) before they can be used in FREQUENCIES. If analytical MCSCF second derivatives have been computed using multi; cpmcscf,hess, FREQUENCIES will use them by default.

CENTRAL

Use central differences/high quality force constants (default).

NUMERICAL

Differentiate the energy twice, using central differences.

FORWARD

Use forward differences/low quality force constants.

SYMM=AUTO|NO

During the numerical calculation of the hessian, the symmetry of the molecule may be lowered. Giving SYMM=AUTO the program uses the maximum possible symmetry of the molecular wavefunction in each energy/gradient calculation, and this option therefore minimizes the computational effort. With SYMM=NO no symmetry is used during the frequency calculation (default). For single reference calculations like HF, MP2, CCSD, RCCSD the AUTO option can be safely used and is recommended. However, the AUTO option cannot be used for multireference methods (MCSCF/MRCI/ACPF/AQCC/RS2). If given, the option is disabled in these cases.

AUTO

Same as SYMM=AUTO, see above.

NOAUTO|NOSYM

Same as SYMM=NO, see above.

HESSREC|SAVE=record

Save hessian to record. By default the hessian is saved on record 5300.2.

FREQREC=record

Save frequencies and normal modes to record (default 5400.2) This information is used, e.g., by the VSCF/VCI program.

TASKREC=record

Save task information in numerical hessian calculation to the given record. This information is required for a restart of a numericaÃl hessian calculation. By default, the information is saved on record 5500.2.

READ

Read hessian from default hessian record.

READ|START=record

Use hessian from previously saved on record. If the hessian has been computed for the current method and geometry already, it is used by default.

RESTART

Attempt to restart a previous numerical frequency/hessian calculation using default task record.

RESTART=record

Attempt to restart a previous numerical frequency/hessian calculation using task record record.

LOW=value

Threshold for printing low frequencies in cm$^{-1}$. If this option is given, frequencies below the given value are not printed. By default, all frequencies are printed.

STEP=value

Determines the step size of the numerical differentiation of the energy or the gradient. The default step size is 0.01 a.u.

MAXTASK=value

Stop the calculation if the number of tasks is exceeded (the calculation can be restarted later).

MAXCPU=value

Stop the calculation if the given CPU-time (in sec) exceeded (the calculation can be restarted later).

NEW

Recompute hessian, even if a hessian is already available.

PROJECT

Project rotations and translations out of the hessian (default).

NOPROJECT

Don't project rotations and translations out of the hessian.

PRINT=value

Print option. If value is greater or equal to zero, the hessian and other information is printed (default $-1$).

DEBUG

Print Debug information, same as PRINT=1.

For compatibility with older MOLPRO versions many of the options can also be set using directives, as described in the following sections.