Explicitly correlated coupled cluster F12 theory with single and double excitations

摘要

Full explicitly correlated F12 coupled cluster theory with single and double excitations and with Slater-type geminal as a correlation factor is introduced and implemented within the standard approximation. The variant "C" that does not require integrals over the commutator between the kinetic operator and the correlation factor has been used. All the necessary integrals are analytically calculated. With variant C also, first results are reported for the correlation factor being the interelectronic distance coordinate, i.e., for original R12 method. Calculations have been performed for a set of eight molecules including CH2((1)A(1)), CH4, NH3, H2O, HF, CO, N-2, and F-2, as well as for the constituting atoms. Atomization energies are reported too. (C) 2008 American Institute of Physics.