Implementation of the CCSD(T)-F12 method using cusp conditions.
The explicitly-correlated coupled-cluster singles and doubles with perturbative triples method (CCSD(T)-F12) is implemented using the cusp conditions. Numerical tests for a set of 16 molecules have shown agreement of correlation energies within 1 mE(h) between the cusp-condition and fully-optimized CCSD(T)-F12 methods. Benchmark calculations on 13 chemical reactions with the cusp-condition CCSD(T)-F12 method reproduce experimental enthalpies within 2 kJ mol(-1). It is also shown that regular unitary-invariant ansatz cannot exactly satisfy singlet and triplet cusp conditions in open-shell situations. We present an extended ansatz which can handle both conditions exactly.
Graduate School of Information Science, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan.
Denis
D
Bokhan
Seiichiro
S
Ten-no
Jozef
J
Noga
D000465:Algorithms; D003198:Computer Simulation; D004735:Energy Transfer; D008956:Models, Chemical; D011789:Quantum Theory; D013816:Thermodynamics