MOLPRO

3 DEFINITION OF MOLPRO INPUT LANGUAGE 8
Here START: is a label, and CCSD(T) is a command.
Strings containing blanks can be entered using quotes. For instance, ’This is a string’
is interpreted as one string, but This is a string is a sequence of four strings in four
subsequent fields. Strings in quotes are not converted to upper case.
Input lines may be concatenated using \ at the end of the line(s) to be continued. Any number
of lines may be concatenated up to a total length of 1024 characters (only 500 characters are
possible on older IBM systems).
Filenames may be up to 31 characters long, provided that long filenames are supported by the
Unix system used. An exception are older CRAY systems, which allow only 8 characters for
the names of binary MOLPRO files.
3.2 Commands
A command invokes a particular program. It may be followed by local input for this program,
enclosed in curley brackets 1
The general format is either
COMMAND, options
or
{ COMMAND,options
directives
data
}
Examples for commands are HF, MP2, CCSD(T), MCSCF, MRCI. Examples for directives
are OCC, CLOSED, WF, PRINT. Directives can be in any order, unless otherwise
noted. Data can follow certain directives. For the format of options, directives and data see
subsections 3.3, 3.5, and 3.6, respectively.
In the following, such a sequence of input will be denoted a command block. Special command
blocks are the geometry and basis blocks.
The options given on the command line may include any options relevant to the current program.
For instance, in DF-LMP2-R12 this could be options for density fitting, local, explicit, and/or
thresholds. Alternatively, options can be specified on individual directives like
DFIT,options
LOCAL,options
EXPLICIT,options
THRESH,options
In these cases, only the options belong to the corresponding directive are valid; thus, if an option
for EXPLICIT would be specified, e.g., on the DFIT directive, an error would result. This error
would be detected already in the input prechecking stage.
1 Depending on the parameter STRICTCHECK in file lib/variable.registry the program may tolerate
directives given after commands without curley brackets. The program checks for ambiguities in the input. A
directive is considered ambiguous if a command or procedure with the same name is known, and the directive
is not in a command block (i.e., no curley brackets are used). STRICTCHECK=0: The input checker tolerates
ambiguous directives if they a are followed by a non ambiguous directive which is valid for the current command.
STRICTCHECK=1: The input checker does not tolerate any ambiguous directives. STRICTCHECK=2: The input
checker does not tolerate any directives outside curley brackets. The default is STRICTCHECK=0, which gives the
maximum possible compatibility to previous Molpro versions.