Spinorbitals, Slater Determinants, and Configuration Interaction

Because single-electron wave functions are approximate solutions to the Schroe-dinger equation, one would expect that a linear combination of them would be an approximate solution also. For more than a few basis functions, the number of possible lineal combinations can be very large. Fortunately, spin and the Pauli exclusion principle reduce this complexity. 

Thus far, we have considered only the space part of one-election orbitals, but each orbital also has a spin part. An electron is desci ibed by foui quantum numbers. An orbital can be written as the product of its space part and its spin part 

Slater showed that spinorbitals, arrayed as a determinant, change sign on election exchange so as to obey the Pauli principle. If we wi ite a linear combination of two spinorbitals as a determinant where we assume the space parts are the same but the spin parts are not the same 

This project will familiarize you with the input necessary to carry out calculations using Program SCF. The concept involved is the reverse of that used in Computer 

In this project, we shall predict the wavelength of the absorption maxima of the same four polyenes using the calculated difference (in units of eV), between the LUMO and HOMO of these four molecules (Fig. 8-6). Bear in mind that this is not an ab initio calculation of wavelengths of maximum absorption, because empirically fitted parameters, Yio exist within the program or are 

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