W2X and W3X-L: Cost-Effective Approximations to W2 and W4 with kJ mol–1 Accuracy

• DOI: 10.1021/acs.jctc.5b00135
• Publication Date: 2015-04-13T19:25:34Z
• Authors: Bun Chan; Leo Radom
• Keywords: 01 natural sciences; 0104 chemical sciences

We have formulated the W2X and W3X-L protocols as cost-effective alternatives to W2 W3/W4, respectively, supplement our previously developed set of W1X W3X procedures. The procedure provides an accurate approximation all-electron scalar-relativistic CCSD(T)/CBS energy, with a mean absolute deviation (MAD) 0.6 kJ mol(-1) from benchmark energies provided by CCSD(T) component in W4 protocol. Such performance is comparable that W2w (0.5 mol(-1)) but comes at significantly lower cost. Comparison computational requirements shows should be applicable systems can treated W1w method. Thus, means for treatment medium-sized such naphthalene. For calculation post-CCSD(T) effects, we propose slight modification method used devised procedure. Our new W3-type protocol (W3X-L) combines this It has MAD values 0.8 W4-11 set, which computationally more demanding W3.2 (0.6 mol(-1)). However, use even relatively modest calculations still represents bottleneck, currently restricts its application up size benzene current computing resources.