Complete report - Donostia International Physics Center - Euskal ...

2011 DIPC Highlight
Homolytic molecular dissociation in
natural orbital functional theory
J.M. Matxain, M. Piris, F. Ruiperez, X. Lopez and J.M. Ugalde
Physical Chemistry Chemical Physics 13, 20129 (2011)
The dissociation of diatomic molecules of the 14-electron isoelectronic series N 2 , O +2 2 , CO, CN – and
NO + is examined using the Piris natural orbital functional. It is found that the method describes correctly
the dissociation limit yielding an integer number of electrons on the dissociated atoms, in contrast to the
fractional charges obtained when using the variational two-particle reduced density matrix method under
the D, Q and G positivity necessary N-representability conditions.
The chemistry of the considered systems is discussed in terms of
their dipole moments, natural orbital occupations and bond orders
as well as atomic Mulliken populations at the dissociation limit. The
values obtained agree well with accurate multiconfigurational wave
function based CASSCF results and the available experimental data.
Astonishing behavior of PNOF5 at the dissociation channel.
It dissociates to integer number of electrons.
In this figure all the relevant information for the dissociation of N 2 is included. Note that the obtained Natural Orbitals
are depicted at the equilibrium region and at the dissociation limit, and that the occupation numbers of
such Natural Orbitals are depicted as a function of the interatomic distance. It is observed that at the dissociation
limit all these orbitals have occupation number 1, and that Natural Orbitals are delocalized in both atoms, which
corresponds to the correct dissociation to two atoms in their ground quartet states. Finally, the dissociacion
curve is also provided.
PNOF5 accounts for non-dynamical electron correlation.
68 DIPC 10/11
DIPC 10/11 69