|Budget Amount *help
¥6,800,000 (Direct Cost : ¥6,800,000)
Fiscal Year 1994 : ¥2,600,000 (Direct Cost : ¥2,600,000)
Fiscal Year 1993 : ¥4,200,000 (Direct Cost : ¥4,200,000)
Single reference perturbation theory and cluster expansion theory such as symmetry adapted cluster and coupled cluster theories are very effective in describing dynamical correlation but fail badly in dealing with nondynamical correlation. CI is easily applied in multireference form and can handle nondynamical correlation but the CI expansion becomes less compact and less efficient as the number of electrons in the system grows. Therefore we have developed multireference based Rayleigh-Schrodinger perturbation theory. The MRMP is reliable and retains the attractive features of the single reference MP method. The theory has conceptual simplicity due to the independent electron pair model. It is almost size consistent. It is very efficient and cost effective. Multireference technique can dissociate a molecule correctly into its fragments. It is applicable to open shells and excited states.
The state-specific MRMP has been sucessfully applied to the calculations of the potential energy surfaces of chemical reactions. Also the theory was applied to the study of valence and Rydberg excitation energies of benzene. The results compare well with the experiment. The calculated valence pi-pi^* excitation energies (experimental values in parentheses) are ^1B_<2u>,4.77 (4.90), ^1B_<1u>,6.28 (6.20), ^1E_<1u>,6.98 (6.94) and ^1E_<2g>,7.88 (7.80) eV,respectively. The Rydberg excitation energies are also predicted with an accuracy of 0.18 eV or better. Results of similar accuracy are obtained for the valence and Rydberg excitation energies for cyclopentadiene, furan, pyrrole, naphthalene and ozone.