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The calculation of electronic charges in molecules using a simplified semiempirical 'atoms in molecules' method
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Evans, Donald Andrew (1974) The calculation of electronic charges in molecules using a simplified semiempirical 'atoms in molecules' method. PhD thesis, University of Warwick.

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Official URL: http://webcat.warwick.ac.uk/record=b1746731~S1
Abstract
This thesis describes an approach to the problem of computing electronic charge distributions in molecules.
The molecule is treated as a collection of atoms in assumed valence states. Sigma and pi electrons are separated from each other. The sigma electron distribution is computed using a valence state scheme the essence of which is a system of orbital charge equations, a unique equation for each type of bond. The form of orbital charge equation for a bond X  Y described by an M.O.
Ψ = ciϕi + cjϕj
where ϕi and ϕj are the bonding A.O.'s (usually hybrid) on X and Y respectively is
N(XY) = kYXNyT  KXYNXT + IXY
where N(XY) is the charge in orbital ϕi in the bond XY. kYX, kXY, IXY are all parameters and NXT, NYT are the total charges on X and Y excluding the charges in ϕi and ϕj.
The interaction of the sigma electrons with the pi electrons is described in two ways. In the first method the interaction occurs through charge dependent inductive parameters hX in the expression
αX = αC + kXβCC
The sigma electron calculation is linked to a H.M.O. calculation to form an iterative method, the iterative selfconsistent charge method  I.S.C.C.M.
In the second approach a P.P.P. (σ + π) method is developed in which the sigma distribution provides a potential framework for the pi electrons. The Wμ terms in the diagonal matrix elements of the P.P.P. method are interpreted as valence state ionisation potentials (V.S.I.P.'s) of the pi orbitals and are expressed as functions of the charge distribution, sigma and pi.
The advantages and disadvantages of the two approaches are discussed and the charges obtained using both methods are compared with other results in the literature.
Item Type:  Thesis (PhD)  

Subjects:  Q Science > QD Chemistry  
Library of Congress Subject Headings (LCSH):  Electric charge and distribution, Molecules  Electric properties  
Official Date:  March 1974  
Dates: 


Institution:  University of Warwick  
Theses Department:  School of Molecular Sciences  
Thesis Type:  PhD  
Publication Status:  Unpublished  
Supervisor(s)/Advisor:  Jenkins, H. Donald Brooke  
Sponsors:  University of Warwick. School of Molecular Sciences ; Science Research Council (Great Britain)  
Extent:  v, 124 leaves  
Language:  eng 
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