[Pw_forum] Methods of analyzing chemical bonds

[Clark Lee]

Hi all,
Recently I learned methods which are now widely used for analyzing the
chemical bonds (Chem.Rev, 2000, 100, 717). Partitioning schemes based on the
electronic charge distribution include the natural bondorbital (NBO),
thecharge distribution analysis (CDA), the atoms-in-molecules (AIM) method.
There are also methods which define the partitioning of the energy of a
chemical bond in different contributions: the energy decomposition analysis
(EDA), the extended transition state (ETS) and the constrained space orbital
variation (CSOV) method.

The basic ideas of the EDA, ETS and CSOV methods are the following.  The
total bond energy ∆E of a bond A-B is partitioned into four components which
are calculated separately in four consecutive steps: ∆E=∆Eprep + ∆Eels +
∆EPauli + ∆Eorb. Like the EDA and ETS methods, the CSOV partitioning scheme
uses the frozen orbitals of the fragments as the starting point for the
energy decomposition by
superimposing them fixed at their separated unit character. Starting from
the superposition of the fragments, the wave function of the complex is
optimized in a series of steps. The energy changes which are associated with
changing the size of the variational space indicate the importance of the
different orbital interactions for the bond energy.

These methods provide insights into the chemical bondings; in contrast,
method like charge density difference is not so effective as these methods.
Here goes my question:  has  any  of these  methods been implemented in  the
QE package? How can I carry out CSOV method in PWscf to study a bonding of
an adsobate-substrate interaction.

Another question: I noticed that electron localizaiton function analysis was
not implemented in previous versions of QE package. I don't know whether it
is included or  not.

-- 
Yours sincerely,

Jibiao Li

State Key Lab of Corrosion and Protection (SKLCP)
Institute of Metal Research (IMR)
Chinese Academy of Sciences (CAS), China
Phone: 024-23904856
Email: jibiaoli at gmail.com
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