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Natural Orbitals (Read 3546 times)
Gerrit-Jan Linker
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Natural Orbitals
18.09.08 at 09:05:08
 
Natural Orbitals
 
Compute properties of molecules is most efficiently done using natural orbitals once the energy and wavefunction has been found. Once natural orbitals have been found the information in the wavefunction has been compressed from a many determinant function down to a set of orbitals and occupation numbers.
 
Properties can be computed by finding the expectation value of the property operator with the natural orbitals weighted by the occupation number of each orbital.
 
Occupation numbers are close to one or two for occupied orbitals. Higher energy orbitals can have a small amount of electron occupation which is rougly analogous to the excited configuration weight.
 
Source:
Computational Chemistry. A practival Guide for Application Techniques to Real World Problems. David. C. Young.
 
Natural orbitals are the eigenfunctions of the first-order reduced density matrix.
 
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Gerrit-Jan Linker
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Gerrit-Jan Linker
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NBO: Natural Bond Orbitals
Reply #1 - 24.05.12 at 19:01:33
 
NBO: Natural Bond Orbitals
 
A natural bond orbital or NBO is a calculated bonding orbital with maximum electron density. The NBOs are one of a sequence of natural localized orbital sets.
 
Atomic orbital → NAO → NHO → NBO → NLMO → Molecular orbital  
 
An NBO can be considered as the Chemist's basis set.  They block diagonalise the one-particle density matrix. From NBO's Natural Localised MO's are formed.
 
NBO analysis:
Natural Bond Order analysis comprises a sequence of transformations of the input basis, the AO's, to various localised basis sets:
NAO's: Natural Atomic Orbitals
NHO's: Natural Hybrid Orbitals
NBO's: Natural Bond Orbitals
NLMO's: Natural Localised Molecular Orbitals
 
These localised basis sets may subsequently be transformed to delocalised natural orbitals (NO's) or canonical molecular orbitals (MO's)
 
 
 
 
Source:
http://en.wikipedia.org/wiki/Natural_bond_orbital
http://pubs.acs.org/doi/abs/10.1021/cr00088a005
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« Last Edit: 24.05.12 at 19:06:06 by Gerrit-Jan Linker »  

Gerrit-Jan Linker
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