Ab initio thermochemistry beyond chemical accuracy for first-and second-row compounds
Abstract
Description
By judicious use of extrapolations to the 1-particle basis set limit and $n$-particle calibration techniques, total atomization energies of molecules with up to four heavy atoms can be obtained with calibration accuracy (1 kJ/mol or better, on average) without any empirical correction. For the SCF energy a 3-point geometric extrapolation is the method of choice. For the MP2 correlation energy, a 2-point $A+B/(l+1/2)^3$ extrapolation is recommended, while for CCSD and CCSD(T) correlation energies we prefer the 3-point $A+B/(l+1/2)^C$ formula. Addition of high-exponent `inner polarization functions' to second-row atoms is essential for reliable results. For the highest accuracy, accounts are required of inner-shell correlation, atomic spin-orbit splitting, anharmonicity in the zero-point energy, and scalar relativistic effects.
43 pages, in upcoming NATO ASI volume "Energetics of stable molecules and reactive intermediates" (ed. M. E. Minas da Piedade)
43 pages, in upcoming NATO ASI volume "Energetics of stable molecules and reactive intermediates" (ed. M. E. Minas da Piedade)