It is also possible to calculate the thermodynamical properties of the molecule. Since MOLPRO can only handle Abelian point groups it is necessary to give the point group of the molecule in the input file:

`THERMO`,[`SYM`=*pointgroup*],[`TEMP`=*value*],
[`PRESS`=*value*],
[`TMIN`=*value*, `TMAX`=*value*, `TSTEP`=*value*]

*pointgroup* has to be the Schoenflies Symbol (e.g. `C3v` for ammonia;
linear molecules have to be `C*v` or `D*h` respectively). If no point group
is given, the point group is determined automatically, but only Abelian groups (D2H and subgroups)
are recognized. If the molecule has higher symmetry this may
eventually cause deviations in the rotational entropy.

The temperature (in K), pressure (in atm) or a range of temperatures (in K) can be given as options.

If no temperature or pressure is specified the zero-point vibrational energy and the enthalpy [kJ/mol], heat capacity [J/mol K] and entropy [J/mol K] are calculated for standard temperature and pressure ( [K], [atm]).

The `FREQUENCIES` program sets the variable `ZPE` containing
the zero-point-energy of the harmonic vibrations in atomic units.
If the `THERMO` option is used, the variables `HTOTAL` and
`GTOTAL`, containing the enthalpy and the free enthalpy of the
system in atomic units, are also set.

molpro@molpro.net 2019-07-16