Linker IT Software
Google
Web www.oraxcel.com
menubar-top-links menubar-top-rechts
Home Help Search Login
Welcome, Guest. Please Login.
SQL*XL: Database to Excel bridge litLIB: Excel power functions pack ExcelLock: Locking and securing your valuable Excel spreadsheets encOffice: Protect your Excel file easy and safe encOffice: Protect your Excel file easy and safe
Pages: 1
primitives, AO's, LCAO and MO's (Read 3435 times)
Gerrit-Jan Linker
YaBB Administrator
*****




Posts: 75
primitives, AO's, LCAO and MO's
31.07.08 at 15:45:41
 
primitives, AO's, LCAO and MO's
 
Starting at the end...
 
MO's are Molecular Orbitals. An MO describes an electron in a molecule. In Hartree Fock calculations the SCF-MO's are calculated and their corrsponding orbital energies.  
 
LCAO. A MO can be constructed as a Linear Combination of Atomic Orbitals: ψ = ∑iciФi
in which ψ is the MO, Фi is an atomic orbital (AO), the sum is over i atomic orbitals and ci is a coefficient that describes how much AO Фi contributes to the MO. The coefficients give a sense of what nature a MO has. What AO's contribute predominantly to the MO?
 
AO's. Atomic Orbitals describes electrons in an atom. Atomic orbitals are often named (s, p, d, f, g, h,...). These letters are derived from the characteristics of their spectroscopic lines: sharp, principal, diffuse, and fundamental, ...
 
Atomic orbitals are in their turn built from primitives. We need certain mathematical functions to start build the orbitals with. Different functions are in use, e.g. Slater type functions, Gaussian type functions... Usually a linear combination is made of different primitive functions to make an AO. The coefficients and primitive function used in these combinations are usually fit to give correct atomic properties.
 
 
 
Back to top
 
« Last Edit: 31.07.08 at 16:06:53 by Gerrit-Jan Linker »  

Gerrit-Jan Linker
Linker IT Software
Email WWW Gerrit-Jan Linker   IP Logged
Gerrit-Jan Linker
YaBB Administrator
*****




Posts: 75
minimal basis approximation
Reply #1 - 11.09.09 at 21:45:23
 
minimal basis approximation
 
In this approximation, the AOs in the MO-LCAO approximation are kept fixed and they can not adjust their shape to the molecular environment.
Back to top
 
 

Gerrit-Jan Linker
Linker IT Software
Email WWW Gerrit-Jan Linker   IP Logged
Pages: 1