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Key Points
Overview
The original Hartree method expresses the total wavefunction of the system as
a product of oneelectron orbitals. In the HartreeFock method, the
wavefunction is an antisymmetrized determinantal product of oneelectron
orbitals (the "Slater" determinant). Schrodinger's equation is transformed
into a set of HartreeFock equations. The HartreeFock approximation is also
known at the selfconsistent field (SCF) method
 begin with a set of approximate orbitals for all the electrons in the system
 one electron is selected, and the potential in which it moves is
calculated by freezing the distribution of all the other electrons and
treating their averaged distribution as the centrosymmetric source of potential
 the Schrodinger equation is solved for this potential, which gives a new orbital for it
 the procedure is repeated for all the other electrons in the system, using
the electrons in the frozen orbitals as the source of the potential
 at the end of one cycle, there are new orbitals from the original set
 the process is repeated until there is little or no change in the orbitals
defined as the wavefunction of an electron in an atom
square of the AO gives the probability density
any electron described by an orbital is said to occupy that orbital
atomic orbitals have a welldefined significance only for hydrogenic atoms
hydrogenic atoms are used in many of the computational approximations
the orbital is a mathematical expression, describing the probability of
finding an electron at some point near the nucleus
 the amplitude of an atomic orbital varies with distance from the nucleus
in a not quite exponential fashion
 generally, MOs are expressed as linear combinations of atomic orbitals
(LCAO), the sum of atomic orbitals centered on each nucleus
the accuracy of the representation of the true molecular orbital as an
LCAO increases with the size of the basis set
 basis set is the number of atomic orbitals employed in the approximation
basic features of LCAO MOs:
 MOs are formed from all the valence orbitals, but do not refer to the
number of electrons that are to be accommodated
 N atomic orbitals overlap to form N molecular orbitals
 for a given set of contributing atomic orbitals, the greater the number of
interatomic nodes, the greater the energy
 the appropriate number of electrons is accommodated in accord with the
rules of the building up principle.
