TY  - JOUR
A1  - Boese, Adrian Daniel
T1  - Basis set limit coupled-cluster studies of hydrogen-bonded systems
JF  - Molecular physics
N2  - As hydrogen-bonded systems are of utmost importance in especially biological and chemical systems, a new set of highly accurate reference dissociation energies, denoted HB49, is devised. For the molecules in this set, the basis set convergence of post-Hartree-Fock methods, including F12 methods, is investigated. Using combined Moller-Plesset perturbation theory (MP2) and CCSD(T) approaches for energies and MP2 and QCISD(T) for gradients, we achieve CCSD(T) accuracy, which has been determined before to yield an accuracy of 0.2 kJ/mol for a subset of HB49. Both conventional extrapolation techniques and F12 techniques are competitive with each other. By using MP2+Delta CCSD(T), a rather fast basis set convergence is obtained when both basis sets are carefully chosen.
KW  - coupled-cluster
KW  - hydrogen bonds
KW  - ab initio
KW  - F12 methods
Y1  - 2015
U6  - https://doi.org/10.1080/00268976.2014.1001806
SN  - 0026-8976
SN  - 1362-3028
VL  - 113
IS  - 13-14
SP  - 1618
EP  - 1629
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Codorniu-Hernandez, Edelsys
A1  - Boese, Adrian Daniel
A1  - Kusalik, Peter G.
T1  - The hemibond as an alternative condensed phase structure for the hydroxyl radical
JF  - Canadian journal of chemistry = Revue canadienne de chimie
N2  - Despite the critical importance of the hydroxyl radical in major scientific fields, there are still open questions on the behavior of this species in the aqueous phase. In particular, there has been much debate on the existence of a hemibonded interaction between the hydroxyl radical and water molecules. While some reports indicate that the hemibonded radical might explain some experimental data, others have claimed that this interaction is simply a density functional theory (DFT) artifact. Here, we provide results from high level (basis set limit of coupled-cluster levels up to single, double, triple excitations (CCSD(T)) and beyond) ab initio calculations of different OH center dot(H2O)(n) clusters in the gas phase to accurately explore the existence of the hemibonded interaction and its energy difference with respect to other well-defined hydrogen bond interactions. Additional comparisons with second order perturbation theory (MP2) and DFT are also presented. Constrained molecular dynamics was applied to determine the free energy for the formation/disruption and ice systems. Overall, our findings confirm that the hemibond can be an alternative structure for the hydroxyl radical in the condensed phase when the formation of hydrogen bonds is impeded. These results will aid the understanding of theoretical and experimental data and help future experimental designs for the detection of this important species.
KW  - hydroxyl radical
KW  - hemibond
KW  - Car-Parrinello
KW  - ab initio
KW  - density functional theory (DFT)
Y1  - 2013
U6  - https://doi.org/10.1139/cjc-2012-0520
SN  - 0008-4042
VL  - 91
IS  - 7
SP  - 544
EP  - 551
PB  - NRC Research Press
CY  - Ottawa
ER  -