Nitrogen 1s binding energies in HN3 and the potassium salts of NO2−, NO3−, and N3− are measured and interpreted in terms of ab initio SCF MO calculations. The valence orbitals must be represented by a double-zeta basis of STO's to adequately interpret the chemical shifts. Inclusion of the lattice potential in the case of the ionic compounds allows a good correlation between calculated and experimental 1s binding energies to be obtained for both ionic and nonionic compounds.

Ab initio self-consistent field molecular orbital calculations of the electronic structures and barriers to internal rotation in hydrogen peroxide and hydrogen persulphide are described using bases of Gaussian type functions. To achieve good agreement with experiment, a basis including p-type functions on the hydrogen atoms is needed for hydrogen peroxide, whilst for hydrogen persulphide a smaller basis is satisfactory. The reasons for this difference axe discussed. Molecular orbital calculations have been successful in describing the barriers to rotation in a number of molecules containing first-rowCalculations near the Hartree-Fock limit and the consideration of distortional effects on rotation have resulted in excellent agreement between the calculated and experimental barriers, (e.g., ethane, computed barrier 3.07 1 kcal/mol, experimental barrier 2.928 k~al/mol).~ Ab initio calculations with small bases, and even semi-empirical calculations have, in many cases given satisfactory quantitative agreement with experiment, and provided insight into the origin of such barriers.'. 2sHowever, with hydrogen peroxide although such calculations do predict a barrier to the cis rotamer, they predict in

AbstractsAlternatives to the Mulliken method of partitioning the overlap charge density in selfconsistent charge molecular-orbital calculations are examined. I t is found that more realistic methods may lead to significantly different self-consistent charges, and different ordering of the electronic energy levels.On discute des alternatives de la mtthode de Mulliken pour partager la densitt de recouvrement dans les calculs des orbitales moltculaires auto-cohtrentes. On trouve que des mCthodes plus rCalistes peuvent donner des charges auto-cohtrentes nettement difftrentes et un ordre difftrent des niveaux d'tnergie tlectroniques.Es wurden Alternativen der Mullikenschen Methode fur die Verteilung der Uberlappungsladungsdichte in scF-Molekulorbitalberechnungen diskutiert. Es wurde gefunden, dass mehr realistische Methoden zu ansehnlich verschiedenen "self-consistent" Ladungen und zu einer verschiedenen Ordnung der elektronischen Energieniveaus fuhren konnen.