Cluster expansion of the wavefunction. Structure of the closed‐shell orbital theory

1978 ◽  
Vol 69 (10) ◽  
pp. 4535-4547 ◽  
Author(s):  
K. Hirao ◽  
H. Nakatsuji
Keyword(s):  
Cluster Expansion ◽  
Closed Shell ◽  
Orbital Theory

scholarly journals LOCALLY PROJECTED MOLECULAR ORBITAL THEORY FOR MOLECULAR INTERACTION WITH A HIGH-SPIN OPEN-SHELL MOLECULE

2006 ◽  
Vol 05 (04) ◽  
pp. 819-833 ◽  
Author(s):  
SUEHIRO IWATA
Keyword(s):  
Molecular Orbital ◽  
High Spin ◽  
Closed Shell ◽  
Open Shell ◽  
Coefficient Matrix ◽  
Molecular Orbitals ◽  
Orbital Method ◽  
Stationary Condition ◽  
Orbital Theory ◽  
Stationary Conditions

Locally projected molecular orbital method for molecular interactions is extended to a cluster consisting of a high-spin open-shell molecule and many closed-shell molecules. While deriving the equations, the Hartee–Fock–Roothaan equation without the orthonormal condition is obtained. The stationary conditions for molecular orbitals are expressed in a form of a generalized Brillouin condition. To obtain the molecular orbital coefficient matrix, which satisfies the stationary condition, a single Fock operator form is presented. For the locally projected molecular orbitals for the open-shell cluster, the working matrix representaion is given.

Many-orbital cluster expansion for the exchange-repulsion energy in the interaction of closed-shell systems

1979 ◽  
Vol 52 (2) ◽  
pp. 93-101 ◽  
Author(s):  
Marek Bulski ◽  
Grzegorz Chałasiński ◽  
Bogumił Jeziorski
Keyword(s):  
Cluster Expansion ◽  
Closed Shell ◽  
Repulsion Energy ◽  
Exchange Repulsion

Electron-spin conservation and methyl-substitution effects on bonds in closed- and open-shell systems — A G3 ab initio study of small boron-containing molecules and radicals

2002 ◽  
Vol 80 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Clement Poon ◽  
Paul M Mayer
Keyword(s):  
Free Radicals ◽  
Bond Strength ◽  
Ab Initio ◽  
Dissociation Energy ◽  
Closed Shell ◽  
Open Shell ◽  
Substitution Effects ◽  
Orbital Theory ◽  
Methyl Substitution ◽  
Bond Strengths

High level ab initio molecular orbital theory calculations have been used to study the geometries and thermochemistry of molecules and free radicals substituted by BH2, BHCH3, and B(CH3)2. The heats of formation and RR'B—X bond strengths (RR' = H, H; H, CH3; CH3, CH3 and X = CH3, NH2, OH, F, SiH3, PH2, SH, and Cl) together with those for the open-shell systems RR'B—Y· (RR' = H, H; H, CH3; CH3, CH3 and Y = CH2, NH, O, SiH2, PH, and S) have been calculated at the G3 level of theory. The trends observed for the homolytic bond strengths in the closed-shell systems are those expected from electronegativity arguments, i.e., as the difference in electronegativity between the two atoms in the B—X bond increases, the bond strength increases. Methyl substitution on B in the closed- and open-shell species increases the ionic contribution to the bond thereby decreasing the bond strength. The lowest possible homolytic dissociation energy for the free radicals RR'BY· is lower than those of their closed-shell counterparts, yet the B—Y· bonds are shorter. This is due to the demands of spin conservation in the dissociation of the radicals favouring the formation of higher energy products.Key words: ab initio calculations, bond dissociation energy, organoboron compounds, thermochemistry.

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