28: The Chemical Bond in Polyatomic Molecules
- Page ID
- 416120
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The structure in space of polyatomic molecules depends on the stereochemistry of their chemical bonds and can be determined by solving the (approximated) TISEq using the Born—Oppenheimer approximation using a method that uses a linear combination of atomic orbitals to form molecular orbitals (LCAO-MO).
- 28.1: The Chemical Bond in the Water Molecule Using a Minimal Basis
- For a minimal representation of the two hydrogen atoms, we need two 1s functions, one centered on each atom. Oxygen has electrons in the second principal quantum level, so we will need one 1s , one 2s , and three 2p functions (one each of px , py , and pz ).
- 28.2: Hartree-Fock Calculation for Water
- To find the Hartree-Fock (HF) molecular orbitals (MOs) we need to solve the following secular determinant.
- 28.3: Shapes and Energies of Molecular Orbitals
- If we analyze the optimized coefficients of the occupied MOs reported in Equation 29.2.10, we observe that the lowest energy orbital (by a lot!) is a nearly pure oxygen 1s orbital since the coefficient of the oxygen 1s basis function is very nearly 1 and all other coefficients are rather close to 0.