MOLPRO

35 RELATIVISTIC CORRECTIONS 268
• The default is not to produce any orbitals or densities, and so only the atomic coordinates
are dumped.
• The default is to use unformatted binary files, and this should not normally be changed.
• The ORIGIN and AXIS commands should not be used.
• If
INTERACT
is given in the input, when all the grids have been calculated, an attempt is made to
start gOpenMol by executing the Unix command rungOpenMol. If rungOpenMol
is not in $PATH, then nothing happens. Otherwise, gOpenMol should start and display
the molecule. Any .plt files produced can be added to the display by following the
Plot;Contour menu item. The name of the Unix command may be changed from the
default rungOpenMol by specifying it as the first argument to the INTERACT directive.
By default, gOpenMol is not started, and this is equivalent to giving the command BATCH.
35 RELATIVISTIC CORRECTIONS
There are three ways in MOLPROto take into account scalar relativistic effects:
1. Use the Douglas-Kroll relativistic one-electron integrals.
2. Compute a perturbational correction using the Cowan-Griffin operator (see section 6.13).
3. Use relativistic effective core potentials (see section 12).
35.1 Using the Douglas–Kroll–Hess Hamiltonian
For all-electron calculations, the prefered way is to use the Douglas–Kroll–Hess (DKH) Hamiltonian,
which is available up to arbitrary order in MOLPRO. It is activated by setting
SET,DKROLL=1
somewhere in the input before the first energy calculation. If no further input is specified, the
standard second-order Douglas–Kroll–Hess Hamiltonian (DKH2) is used.
Starting with version 2006.1, MOLPRO does, however, also provide the DKH Hamiltonian up to
(in principle) any arbitrary order of decoupling (DKHn). The desired DKH order (DKHO) and
the chosen parametrization for the unitary transformations have to be specified by
SET,DKHO=n, (n = 2,...,12),
SET,DKHP=m, (m = 1,...,5)
below the DKROLL=1 statement in the input file. Alternatively, these values can be given as
options on the INT command:
INT,DKROLL=1,DKHO=n,DKHP=m.
The possible parametrizations supported by MOLPRO are:
DKHP=1:
DKHP=2:
Optimum parametrization (OPT, default)
Exponential parametrization (EXP)