In the first sentence of this Introduction to MOLPRO, MOLPRO is described as a "system of programs", not just one program.
The first link you provided is for the program called MULTI
for MCSCF calculations (which includes multiple types of MCSCF such as CASSCF and RASSCF). The second link you provided is for the program called MRCI
. Each program in MOLPRO can have different authors, and you can see that the 9 papers listed in the MULTI
program bibliography don't overlap (not even in the years published!) with the 8 papers listed in the MRCI
program bibliography, except for the 1987 book chapter which is more of a review of papers previous to that. How things work in one MOLPRO program won't always be the same as in other MOLPRO programs. Some names of things are overloaded, so that the same string is used in multiple programs, but not necessarily with exactly the same meaning.
When I search expec2
in the documentation link you provided for the MRCI
program, the only appearance of that string on that page occurs in a MULTI
command:
{multi;
occ,3,1,1;frozen,1;wf,6,1;state,3;lquant,0,2,0;wf,6,4;lquant,2;
tran,lz;
expec2,lzlz;}
Interestingly, they used lzlz
instead of lzz
for the $\hat{L}_z^2$ operator, as described here.
I don't see any example of how to use expec2
with the MRCI
program, and the introduction to the MRCI
documentation to which you provided the link, says
"The EXPEC
directive allows to compute expectation values over one-electron operators, and the TRAN
directive can be used to compute transition matrix elements for one-electron properties"
but nothing about 2-electron properties such as the ones available in MULTI
by using the EXPEC2
card. If you search the word "properties" in the MRCI
documentation, you'll find that there's a sub-section about one-electron properties, but nothing suggesting that two-electron properties are possible.