On the Additivity of the Molecular Second Moments of Charge and Diamagnetic Susceptibility

It was shown that the application of the additivity rules [Chem. Phys. Letters 13 (1972) 571] may be very helpfull for the determination of the sign of the g tensor

Semiempirical Study of Intramolecular Hyclrogen Bond in 6-Hydroxy-2-formylfulvene and 9-Hydroxyphenalenone

It is shown that semiempirical MINDO/3, MNDO and AMI methods are very useful in discussing intramolecular hydrogen . bonding in sizeable systems. The present results indicate that intramolecular H-bonds in 6-hydroxy-2-formylfulvene and 9-hydroxyphenalenone are asymmetric, in fuU accordance with ESCA observations and DQCC measurements. The former molecule should exhibit a stronger H-bond. On the other hand, the barrier height for proton tunnelling is higher in the latter compound. Relative stabilities of various species are interpreted by employing the energy partitioning technique

Molecular Second Moments and Diamagnetic Susceptibilities. Reparametrization of the Independent Atom Model Formulas

The independent atom model (IAM) is applied to the calculation of molecular second moments and diamagnetic susceptibilities. The earlier formulas are generalized and better agrement with experimental data and ab initio results is achieved

Semiempirical Studies of Inner-Core Energy Levels. Part 7. ESCA Shifts of Germanium in Molecular Systems

Shifts of the 3p213 ene;.·gy levels of germanium in different chemical moieties were studied by using the semiempirical SCC-MO method. The calculations were performed within the framework of the electrostatic potential method in the point-charge approximation. Relaxation energies were explicitly taken into account by employing the equivalent core and transition potential methods. It was found out that the relaxation energy plays a decisive role in determining shifts along the series GeH4--+ Ge(CHak The results obtained by the equivalent core and transition potential methods are similar being in the same time in good agreement with experiment. Performance of various semiempirical schemes in evaluating ESCA shifts is briefly discussed

On the Pairwise Nonorthogonality Problem in Quantum Chemistry

It is shown that, starting from a set of local hybrid orbitals if>; (i = 1, . .. n) one can construct pairwise nonorthogonal set of functions Xi (i = 1, ... n) with the following feature calculated by employing maximum overlap criterion or by max,imizim. g the average distance between the centroids of charge of the electronic pairs. The use of the pairwise nonorthogonal functions is advantageous in semiempirical methods since it minimizes the error introduced by the neglect of the many-center electron repulsion integrals

Empirical Calculation of the Diamagnetic Susceptibility of Molecules

Recent development of experimental microwave spectroscopy1 and ab initio oomputational techniques based on Gaussian atomic funciti0!!1:S 2 have made aV\u27ailable values of diamagnetic susceptibilities and individual second moments of the electronic charge distributtons for a large IIlUmber of molecules. The analysis of the experimental results have led Blickensderfer et al.3 to the development of empirical rules for the .out-of plane second moments for plranar molecules involving first row atoms and hydrogens. These empirical rules were later rationalized within the zer.o-differential .overlap approximation at the CND0/2 level of sophi:stica1tion4• Subse.quently, iit was shown that simrilar additivi·ty rules hold for in plane second moments and 1f .they are calculated fiirst <in the point charge approximation

The Calculation of Molecular Quadrupole Moments in Some Fluorine Containing Compounds by the SCC Method

Sec (self-consistent charge) method was applied to a series of related fluorinated hydrocarbons. The calculated anisotropies of the second moments of the charge and the molecular quadrupoles are in fairly good agreement with experimental data. The results indicate that coulomb repulsion between electrons are absorbed· satisfactorily into the parameterization of the sec method