CFOUR | Main / Cfour Keyword Section

In this section, keywords are given to specify the type of calculation to be performed with CFOUR.

The keyword list starts with *CFOUR(, is followed by the actual keywords, and ends with a closing parentheses ). Each keyword (for a list of all possible keywords, see ) consists of the name of the keyword followed by an equal sign and the value, task, etc. to be assinged to this keyword. E.g., for the specification of the quantum chemical method, the keyword is CALC_LEVEL. Possible values for this keyword are, for example,HF, MP2, CCSD, CCSD(T), etc. In the keyword list, one thus specifies for example

CALC_LEVEL=CCSD(T)

in order to requests a CCSD(T) calculation. Other keywords, e.g. the keyword CC_MAXCYC needed to specify the maximum number of iterations in the solution of the CC equations, require an integer input, such as, for example:

CC_MAXCYC=50

Note that the various keywords are separated by a comma. The list of keywords can be continued on a new lines (there is no limit to the maximum number of lines to be used). In this case the last keyword on a line should not be followed by a comma (the separation is invoked by the line break) and it should be noted that a closing parentheses should be given only on the last line.

Additional tips

Note that in many cases, a short version of the keyword, e.g. CALC for CALC_LEVEL is also acceptable.

As to all keywords meaningful default values have been assigned, only a few keywords need to be specified in most calculations.

A complete list of the available keywords can be found here.