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Addition and Subtraction of Electrons


Excitation energies can be found by taking the difference between the ground state energy of systems with different numbers of electrons. For example, a gap energy tex2html_wrap_inline7955 can be written as


where tex2html_wrap_inline7957 is the energy to add an electron (the electron affinitygif) and tex2html_wrap_inline7963 is the energy to remove an electron (the ionization potential).

To obtain an estimate of the electron(hole) energies, tex2html_wrap_inline7965 , within a QMC calculation, all that is required is to include (remove) the corresponding conduction (valence) orbital in the Slater Determinant part of the trial wavefunction given in Eq.(gif). The tex2html_wrap_inline6593 -point at which the electron(hole) energy is calculated, is determined by the tex2html_wrap_inline6593 -value of this conduction (valence) orbital.

Andrew Williamson
Tue Nov 19 17:11:34 GMT 1996