ELECTRONIC POTENTIAL SURFACES OF ACETYLENE IN LCAO/MO APPROXIMATION

Abstract

A digital computer has been programmed to carry out 6-electron LCAO/ASMO calculations for linear and trans-bent acetylene, with the following input variables; coefficients of the LCAO/MOs, carbon–carbon bond length, and effective nuclear charge on the carbon atoms. The effect of varying these parameters upon the calculated electronic energy levels is discussed, and approximations to "best" MOs are obtained for various states of the molecule, leading to values of hybridization parameters for the carbon atoms. Certain assumptions enable the electronic energies to be related to the C—C—H bending angle; from this it is concluded the ground state is linear and the lowest A_u excited state is bent, in accordance with experiment. Values are given for electronic transition energies and hydrogen-bending force constants.