dorsal/arxiv
View SchemaW3 theory: robust computational thermochemistry in the kJ/mol accuracy range
| Authors | A. Daniel Boese, Mikhal Oren, Onur Atasoylu, Jan M. L. Martin, Mihaly Kallay, Juergen Gauss |
|---|---|
| Categories | |
| ArXiv ID | physics/0311067 |
| URL | https://arxiv.org/abs/physics/0311067 |
| DOI | 10.1063/1.1638736 |
| Journal | Journal of Chemical Physics 120, 4129-4141 (2004) |
Abstract
We are proposing a new computational thermochemistry protocol denoted W3 theory, as a successor to W1 and W2 theory proposed earlier [Martin and De Oliveira, J. Chem. Phys. 111, 1843 (1999)]. The new method is both more accurate overall (error statistics for total atomization energies approximately cut in half) and more robust (particularly towards systems exhibiting significant nondynamical correlation) than W2 theory. The cardinal improvement rests in an approximate account for post-CCSD(T) correlation effects. Iterative T_3 (connected triple excitations) effects exhibit a basis set convergence behavior similar to the T_3 contribution overall. They almost universally decrease molecular binding energies. Their inclusion in isolation yields less accurate results than CCSD(T) nearly across the board: it is only when T_4 (connected quadruple excitations) effects are included that superior performance is achieved. $T_4$ effects systematically increase molecular binding energies. Their basis set convergence is quite rapid, and even CCSDTQ/cc-pVDZ scaled by an empirical factor of 1.2532 will yield a quite passable quadruples contribution. The effect of still higher-order excitations was gauged for a subset of molecules (notably the eight-valence electron systems): T_5 (connected quintuple excitations) contributions reach 0.3 kcal/mol for the pathologically multireference X ^1\Sigma^+_g state of C_2 but are quite small for other systems. A variety of avenues for achieving accuracy beyond that of W3 theory were explored, to no significant avail. W3 thus appears to represent a good compromise between accuracy and computational cost for those seeking a robust method for computational thermochemistry in the kJ/mol accuracy range on small systems.
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"abstract": "We are proposing a new computational thermochemistry protocol denoted W3\ntheory, as a successor to W1 and W2 theory proposed earlier [Martin and De\nOliveira, J. Chem. Phys. 111, 1843 (1999)]. The new method is both more\naccurate overall (error statistics for total atomization energies approximately\ncut in half) and more robust (particularly towards systems exhibiting\nsignificant nondynamical correlation) than W2 theory. The cardinal improvement\nrests in an approximate account for post-CCSD(T) correlation effects. Iterative\nT_3 (connected triple excitations) effects exhibit a basis set convergence\nbehavior similar to the T_3 contribution overall. They almost universally\ndecrease molecular binding energies. Their inclusion in isolation yields less\naccurate results than CCSD(T) nearly across the board: it is only when T_4\n(connected quadruple excitations) effects are included that superior\nperformance is achieved. $T_4$ effects systematically increase molecular\nbinding energies. Their basis set convergence is quite rapid, and even\nCCSDTQ/cc-pVDZ scaled by an empirical factor of 1.2532 will yield a quite\npassable quadruples contribution. The effect of still higher-order excitations\nwas gauged for a subset of molecules (notably the eight-valence electron\nsystems): T_5 (connected quintuple excitations) contributions reach 0.3\nkcal/mol for the pathologically multireference X ^1\\Sigma^+_g state of C_2 but\nare quite small for other systems. A variety of avenues for achieving accuracy\nbeyond that of W3 theory were explored, to no significant avail. W3 thus\nappears to represent a good compromise between accuracy and computational cost\nfor those seeking a robust method for computational thermochemistry in the\nkJ/mol accuracy range on small systems.",
"arxiv_id": "physics/0311067",
"authors": [
"A. Daniel Boese",
"Mikhal Oren",
"Onur Atasoylu",
"Jan M. L. Martin",
"Mihaly Kallay",
"Juergen Gauss"
],
"categories": [
"physics.chem-ph",
"physics.comp-ph"
],
"doi": "10.1063/1.1638736",
"journal_ref": "Journal of Chemical Physics 120, 4129-4141 (2004)",
"title": "W3 theory: robust computational thermochemistry in the kJ/mol accuracy range",
"url": "https://arxiv.org/abs/physics/0311067"
},
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