Heats of formation of perchloric acid, HClO$_4$, and perchloric anhydride, Cl$_2$O$_7$. Probing the limits of W1 and W2 theory
| dc.creator | Martin, Jan M. L. | |
| dc.date | 2005-08-11 | |
| dc.date.accessioned | 2026-07-07T06:31:35Z | |
| dc.date.available | 2026-07-07T06:31:35Z | |
| dc.description | The heats of formation of HClO$_4$ and Cl$_2$O$_7$ have been determined to chemical accuracy for the first time by means of W1 and W2 theory. These molecules exhibit particularly severe degrees of inner polarization, and as such obtaining a basis-set limit SCF component to the total atomization energy becomes a challenge. (Adding high-exponent $d$ functions to a standard $spd$ basis set has an effect on the order of 100 kcal/mol for Cl$_2$O$_7$.) Wilson's aug-cc-pV(n+d)Z basis sets represent a dramatic improvement over the standard aug-cc-pVnZ basis sets, while the aug-cc-pVnZ+2d1f sequence converges still more rapidly. Jensen's polarization consistent basis sets still require additional high-exponent $d$ functions: for smooth convergence we suggest the \{aug-pc1+3d,aug-pc2+2d,aug-pc3+d,aug-pc4\} sequence. The role of the tight $d$ functions is shown to be an improved description of the Cl (3d) Rydberg orbital, enhancing its ability to receive back-bonding from the oxygen lone pairs. In problematic cases like this (or indeed in general), a single SCF/aug-cc-pV6Z+2d1f calculation may be preferable over empirically motivated extrapolations. Our best estimate heats of formation are $ΔH^\circ_{f,298}[$HClO$_4$(g)$]=-0.6\pm$1 kcal/mol and $ΔH^\circ_{f,298}[$Cl$_2$O$_7$(g)$]=65.9\pm$2 kcal/mol, the largest source of uncertainty being our inability to account for post-CCSD(T) correlation effects. While G2 and G3 theory have fairly large errors, G3X theory reproduces both values to within 2 kcal/mol. | |
| dc.description | J. Mol. Struct. (THEOCHEM), in press (WATOC'05 special issue) | |
| dc.identifier | https://arxiv.org/abs/physics/0508076 | |
| dc.identifier | http://arxiv.org/abs/physics/0508076 | |
| dc.identifier | J. Mol. Struct. (THEOCHEM) 771, 19-26 (2006) | |
| dc.identifier | doi:10.1016/j.theochem.2006.03.035 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/98650 | |
| dc.subject | Chemical Physics | |
| dc.subject | Computational Physics | |
| dc.title | Heats of formation of perchloric acid, HClO$_4$, and perchloric anhydride, Cl$_2$O$_7$. Probing the limits of W1 and W2 theory | |
| dc.type | text |