Convergence of triples energy in CCSD(T) and CC3 calculations with correlation-consistent basis sets

摘要

The convergence behavior of connected triples correlation energy in CCSD(T) and CC3 calculations with (aug-)cc-pVXZ basis sets has been accurately described in terms of a power law of the type E-X=E-infinity+AX(-4). Calculations ranging from double-Z through septuple-Z attest the validity of this X-4 convergence model. Extrapolations generated from (X-1,X)-Z calculations yield energies of nearly (X+1)-Z quality. Typically, the fraction of triples correlation energy recovered is 0.92+/-0.05 in (D,T) extrapolations; 0.98+/-0.01 in (T,Q) extrapolations; 1.0002+/-0.0012 in (Q,5) extrapolations; and 0.9995+/-0.0005 in (5,6) extrapolations. (C) 2004 American Institute of Physics.