CCL: ADF-Bond energy analysis query

["Belkhiri, lotfi" <lotfi.belkhiri(~)umc.edu.dz>]

Dear ADF user,

ADF is one of the rare quantum chemistry programs which allows a correct decomposition Bond Energy analysis, especially, for fragment-fragment calculations, i.e., for a special bond formation or like for metal-ligand interactions.

In ADF,bond energy decomposition analysis, is based on the transition-state method developped by Ziegler and Morokuma et al. and reveals to be a very useful theoretical tool for predicting and investigating frag-frag bonding interactions and their covalent or ionic character.

Within this scheme, the resulting total bonding energy or energy fragment ÎE_frag obtained from spin restricted or unrestricted calculations, can be decomposed mainly into two terms as follow:

ÎE_frag = E_steric + E_orb

where E_steric term is the steric interaction energy between the (RCp)₃M metallic fragment and azine ligand and E_orb is the orbital (covalent) contribution to the metal-azine bond. The steric energy term (E_steric) is itself decomposed into a destabilizing term E_Pauli, the electronic repulsion due to the Pauli principle, and E_ES, the stabilizing electrostatic energy between the two fragments :

E_steric = E_Pauli + E_ES

However, it is important to remind the ADF users, that this energetic decomposition is not meaningful for a rigorous thermodynamic analysis (enthalpy-entropy parameters), but should be applied to compare the relative stability of the molecules or a specif bond formation.

to be continued...

Lotfi

2013/1/31 sonam bhatia sonamalerts^^^gmail.com <owner-chemistry,ccl.net>

Sent to CCL by: "sonam Âbhatia" [sonamalerts|,|gmail.com]
Dear all,

I am interested in performing Bond energy analysis by use of ADF. I got
Âwindows version installed in our lab but I am the only one in our
group using this software. As we purchased it recently and I am new to it
so learning its basics. I am not quite confident in performing bond energy
analysis by it. As I have performed Geometry optimization of Ph3=C=Ph3
system and in .out file in bond energy decomposition section:
E pauli repulsion
E steric interaction
E orbital interaction

above mentioned values comes.
I suppose interpretation of these values give us bond energy analysis.
Whether I am right?
1) But if suppose i have to do this analysis for particular no. of bonds
like in Ph3=C=Ph3 system for P=C only so how I will specify this?
2) Moreover have you used *occupation* keyword in adf which is used to
specify particular electronic state to individual atom.
3) if suppose for above system I have to give Âs2, p-sigma2, p-pie0
(perpendicular), p-pie0 (parallel) electronic configuration to carbon atom,
then how with the help of occupation keyword I can assign this electronic
configuration.
4) While performing bonding analysis is it mandatory to give ETS-NOCV
calculations?

Please help me in this regard.



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--

Pr. Lotfi Belkhiri
Directeur de Recherches -ÂGroupe de Chimie ThÃorique et ModÃlisation

Unità de Recherche CHEMS - Università Mentouri de Constantine
jct9_cne2010,yahoo.fr
Fax : +213 (0)31 68 15 45
Homepage :Âhttp://www.umc.edu.dz/vf/Labo/FacScienceExact/site_lacmom/crbst_21.html