The FCIQMC program exists through an interface to the NECI codebase,
which is actively developed in the group of A. Alavi, and has been integrated in
the MOLPRO code.
The FCIQMC method is a recently introduced stochastic method which can calculate
principle FCI-quality energies for small to medium-sized molecules.
G. H. Booth, A. J. W. Thom, and A. Alavi, J. Chem. Phys. 131, 054106 (2009);
D. M. Cleland, G. H. Booth, and A. Alavi, J. Chem. Phys. 134,
G. H. Booth, D. M. Cleland, A. J. W. Thom, and A. Alavi, J. Chem. Phys. 135, 084104 (2011).