W1CEP theory for computational thermochemistry

W1 theory is characterized by a rigorous well-defined series of ab initio calculations not explicitly including any empirical adjustment based on experimental results. To expand its applicability to large molecules, a compact effective pseudopotential was included in its computational procedure and the combination is referred to as W1CEP. The values obtained by W1CEP are very close to the original W1 theory, with a mean absolute deviation of 1.2 kcal mol(-1) for W1 and of 1.4 kcal mol(-1) for W1CEP. The range of the deviations with a 95% confidence interval are +/- 3.4 kcal mol(-1) for W1 and +/- 4.0 kcal mol(-1) for W1CEP. In addition to accuracy of the results, another important result is that the calculations using W1CEP decrease the CPU time by 13-30%. (C) 2015 Elsevier B.V. All rights reserved.