Forced Bonding and QTAIM Deficiencies: A Case Study of the Nature of Interactions in He@Adamantane and the Origin of the High Metastabilityстатья
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Дата последнего поиска статьи во внешних источниках: 2 мая 2014 г.
Аннотация:Calculations within the
framework of the interacting quantum
atoms (IQA) approach have shown
that the interactions of the helium
atom with both tertiary, tC, and secondary,
sC, carbon atoms in the metastable
He@adamantane (He@adam) endohedral
complex are bonding in
nature, whereas the earlier study performed
within the framework of
Baders quantum theory of atoms in
molecules (QTAIM) revealed that only
He···tC interactions are bonding. The
He···tC and He···sC bonding interactions
are shown to be forced by the
high pressure that the helium and
carbon atoms exert upon each other in
He@adam. The occurrence of a bonding
interaction between the helium and
sC atoms, which are not linked by a
bond path, clearly shows that the lack
of a bond path between two atoms
does not necessarily indicate the lack
of a bonding interaction, as is asserted
by QTAIM. IQA calculations showed
that not only the destabilization of the
adamantane cage, but also a huge internal
destabilization of the helium atom,
contribute to the metastability of
He@adam, these contributions being
roughly equal. This result disproves
previous opinions based on QTAIM
analysis that only the destabilization of
the adamantane cage accounts for the
endothermicity of He@adam. Also, it
was found that there is no homeomorphism
of the 1(r) and -v(r) fields of
He@adam. Comparison of the IQA
and QTAIM results on the interactions
in He@adam exposes other deficiencies
of the QTAIM approach. The reasons
for the deficiencies in the QTAIM approach
are analyzed.