Lecture 10. Chemical Bonding. Generalization & Matrix Representation References Engel Ch.12, Ratner & Schatz, Ch.11 Quantum Chemistry, McQuarrie, Ch.9 Molecular Quantum Mechanics, Atkins & Friedman (4th ed. 2005), Ch.8 Computational Chemistry, Lewars (2003), Ch.4 A Brief Review of Elementary Quantum Chemistry
LCAO-MO Molecular wave function in HF approximation = Antisymmetrized product (Slater determinant) of one-electron molecular wave functions (molecular orbitals)
Basis set
LCAO-MO Approximation (Linear Combination of Atomic Orbitals for Molecular Orbital)
LCAO-MO Example: Hydrogen (H 2 ) Molecule
Color indicates the sign (+/ ) of the coefficient. Size indicates the magnitude of the coefficient. No node in bonding region Node in bonding region No node in bonding region Bigger contribution Node in bonding region 13.6 eV 16.0 eV 9.2 eV 13.6 eV 18.9 eV 19.6 eV 10.3 eV Homonuclear vs. heteronuclear diatomic molecules
Heteronuclear diatomic molecule: MO diagram of HF
Rearrange and differentiate
→ Matrix diagonalization problem
LCAO-MO & HF Equation: Roothaan-Hall Equation Fock matrix F & Overlap matrix S
Non-linear Integro-Differential equation Linear Algebra Matrix equation
Hartree-Fock-Roothaan-Hall equation (Summary) where MO (one-electron) MOAO H = E where n-electron Wave function Fock operator Hamiltonian operator LC where Fock matrix overlap matrix
Hartree-Fock-Roothaan-Hall equation Overlap matrix element Secular equation Fock matrix element