2020-07-09T20:12:09Z
https://digital.csic.es/dspace-oai/request
oai:digital.csic.es:10261/211469
2020-05-15T11:12:00Z
com_10261_14181
com_10261_4
col_10261_14182
Valentín-Rodríguez, Mónica A.
Bartolomei, Massimiliano
Hernández, Marta I.
Campos-Martínez, José
Hernández-Lamoneda, Ramón
2020-05-15T11:12:00Z
2020-05-15T11:12:00Z
2020-05-11
Journal of Chemical Physics 152:184102 (2020)
0021-9606
http://hdl.handle.net/10261/211469
10.1063/5.0005171
1089-7690
http://dx.doi.org/10.13039/501100003141
The properties of molecular oxygen including its condensed phases continue to be of great relevance for the scientific community. The
richness and complexity of its associated properties stem from the fact that it is a very stable diradical. Its open-shell nature leads to low-lying
multiplets with total electronic spin S = 0, 1, 2 in the case of the dimer, (O2)2, and the accurate calculation of the intermolecular potentials
represents a challenge to ab initio electronic structure methods. In this work, we present intermolecular potentials calculated at a very high
level, thus competing with the most accurate restricted potentials obtained to date. This is accomplished by drawing on an analogy between
the coupled and uncoupled representations of angular momentum and restricted vs unrestricted methodologies. The S = 2 state can be well
represented by unrestricted calculations in which the spins of the unpaired electrons are aligned in parallel; however, for the state where they
are aligned in antiparallel fashion, it would seem that the total spin is not well defined, i.e., the well-known spin contamination problem. We
show that its energy corresponds to that of the S = 1 state and perform unrestricted coupled cluster calculations for these two states. Then, we
obtain the S = 0 state through the Heisenberg Hamiltonian and show that this is very reliable in the well region of the potentials. We make
extensive comparisons with the best restricted potentials [Bartolomei et al., Phys. Chem. Chem. Phys. 10(35), 5374–5380 (2008)] and with
reliable experimental determinations, and a very good agreement is globally found.
eng
openAccess
An unrestricted approach for the accurate calculation of the interaction potentials of open-shell monomers: The case of O2–O2
artículo