AbstractsThis paper examines the relationship between the topographical features of a molecular charge distribution and the kinetic energy of the system. Specifically, the spatial contributions to the kinetic energy are related to the Laplacian of the total charge density and to the gradients of the natural-orbital densities. It is concluded that a necessary requirement for molecular stability is the existence of a net negative curvature for the molecular charge distribution in the internuclear region. It is shown that the charge density accumulated in the internuclear region of a stable molecule is distributed in such a way as to keep the accompanying increase in the kinetic energy to a minimum. A comparison of the contributions to the kinetic energy from the atomic and molecular charge distributions indicates that in the formation of a stable molecule the contribution from the molecular charge density in the binding region is decreased relative to that of the atoms.Dans cet article on examine la relation entre les caracttristiques topographiques d'une distribution de charge molkculaire et l'tnergie cinttique du systtme. Les contributions d'espace de l'tnergie cinttique ont rapport au Laplacien de la densitt de charge totale et aux gradients des densitts des orbitales naturelles. Une condition ntcessaire pour la stabilitt moltculaire est l'existence d'une courbure ntgative nette pour la distribution de charge moltculaire dans la rtgion internuclkaire. On dkmontre que la densitt de charge accumulke dans la rtgion internucltaire d'une moltcule stable est distribute de telle faqon que l'augmentation correspondante de l'tnergie cinttique soit minimiste. Une comparaison des contributions B 1'Cnergie cinktique des distributions de charge atomiques et moltculaires indique, que dans la formation d'une molkcule stable, la contribution de la densitt de charge molkculaire dans la rtgion liante est diminute par rapport A celle des atomes.In diesem Artikel wird die Beziehung zwischen den topographischen Eigenschaften einer molekularen Ladungsverteilung und der kinetischen Energie des Systems untersucht. Die Raumbeitrage zur kinetischen Energie stehen mit dem Laplace-operator der totalen Ladungsdichte und mit den Gradienten der Dichten der naturlichen Orbitalen in Verbindung. Eine notwendige Bedingung fur molekulare Stabilitat ist die Existenz einer negativen Krummung fur die molekulare Ladungsverteilung in der zwischenmolekularen Region. Es wird gezeigt, dass die in der zwischenmolekularen Region angehauftete Ladungsdichte eines stabilen Molekuls in so einer Weise verteilt ist, dass der begleitende Zuwachs der kinetischen Energie minimisiert sei. Ein Vergleich der Beitrage zur kinetischen Energie der atomaren und molekularen Ladungsverteilungen deutet an, dass in der Bildung eines stabilen Molekiils der Beitrag der molekularen Ladungsdichte in dem Bindungsbereich bezuglich auf den der Atome vermindert ist.

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Hartree-Fock and limited configuration interaction calculations were used to investigate the 5Σ+ and related states of FeO with equilibrium separation of [inverted lazy s] 3.2 bohr. Very extended configuration interaction calculations were then performed to determine the properties of the lowest 5Σ+ state. This lowest state is determined to be close to the Hartree-Fock state investigated. The dissociation energy is estimated to be 2.00 ± 0.14 eV. It is concluded that the ground state of FeO is not 5Σ+.

ABSTRACT. A theoretical method, which allows one to d e t e r m i~~e the effect of the Pauli exclusioll principle on the electron density distribution, is used to test the concepts i~nderlying the electron pair repulsion thcory of molecular geometry. I t is shown that pictures of overlapping orbitals frequently do not correspond to the actual effect which the Pauli principle has on the three-dimensional charge density. An alternative electrostatic approach, involving the concept of a binding region for a polyatornic rnolccule, is proposed to account for the observed molecular geometries. INTRODUC'I'IONA theory of lnolecular geometry has been advanced "on the idea that the arrangement of all the electron pairs (bonding pairs and lone pairs) in the valency shell of the central atom is deterinined by the operation of the Pauli exclusion principle (I)". This theory relates the electron distribution in three-dimensional space and thus the ~nolecular geometry to "Pauli repulsions" between pairs of electrons, the pairs being in bond or loile pair orbitals. Lone pairs of electrons, since they are considered t o be in the field of principally one nucleus, are considered as occupying a more diffuse orbital than the bonding electron pairs. 'Thus one speaks of lone pair -lone pair repulsiorls as being greater than lone pair -bond repulsions which in turn are more important than bond-bond repulsions. I t is the purpose of the present work to find a theoretical basis for the concept of "Pauli repulsions" when applied in this manner.The Pauli principle in its most general for111 demands that a wave function be antisymmetric with respect to permuting the space and spill coordinates of all the electroils present in the system. When an orbital approximati011 to the \yave function is employed, the demands of the Pauli principle are inet if no more than two electrons with opposite spins are placed in any one space orbital when these orbitals form an orthogonal set. Indeed, \\+thin the orbital approximation, this is an alternative statement of the I'auli principle. The iiiiportaiit feature for the present discussion is that the Pauli principle demands that the set of orbitals, atomic or niolecular, used to describe the systeln be ortl~ogonal, 111S d r = 6il.

AbstractsThe electrostatic potential V(r) arising from the ab initio LCAO-MO-SCF wave functions of chlorpromazine ( c p z ) and promazine (PZ) has been calculated and discussed. In this approximation, the most probable sites of attack and reaction paths of electrophilic reagents are pointed out and compared. The analysis of V(r) shows that the phenothiazine group has strong nucleophilic properties which are influenced by the phenothiazine substituent and that the electrostatic reactivity of CPZ and PZ is decidedly different near the phenothiazine substituent and similar near the side chain N atom. The dependence of V(r) on the accuracy of the wave function has also been discussed by comparing some ab initio results on pyrrole, pyrazole, and imidazole obtained with a large basis set with an ab initio minimum basis set and with CNDO calculations.Le potentiel Clectrostatique V(r) obtenu par des fonctions d'onde de type LCAO-MO-SCF ab initio pour la chlorpromazine (CPZ) et la promazine (PZ) est discutt. Les sites d'attaque les plus probables et les routes de rtaction de reactants tlectrophiles sont indiquts et comparts. L'analyse de V(r) montre que le groupe phknothiazine a des proprittts nucltophiles fortes, qui sont influendes par le substituant de la phtnothiazine et que les rCactivitts de CPZ et PZ sont remarquablement difftrentes prts du substituant du phtnothiazine mais semblables prts de l'atome d'azote de la chahe de c8tt. On discute aussi la dtpendance de V(r) de la prtcision de la fonction d'onde en comparant quelques rtsultats ab inifio pour le pyrrol, le pyrazole et I'imidazole obtenus avec des jeux de base diffkrents et des rtsultats obtenus par des calculs CNDO.Das von LCAO-MO-SCF-Wellenfunktionen von ab initio-Typ fur Chloropromazin (CPZ) und Promazin (PZ) erhaltene elektrostatische Potential V(r) wird diskutiert. Die wahrscheinlichsten Angriffsplatze und Reaktionspfade elektrophiler Reagenten werden angedeutet und verglichen. Die Analyse von V(r) zeigt, dass die Phenothiazingruppe starke nukleophile Eigenschaften hat, die vom Phenothiazinsubstituent beeinflusst werden und dass die elektrostatischen Reaktivitaten von CPZ und PZ in der Nahe vom Phenothiazinsubstituent ganz verschieden aber in der Nahe vom N-Atom der Seitenkette ahnlich sind. Die Abhangigkeit von V(r) von der Genauigkeit der Wellenfunktion ist auch durch Vergleich einiger abinitio-Ergebnisse mit verschiedenen Basissatzen fur Pyrrol, Pyrazol und Imidazol mit entsprechenden CNDO-Resultaten diskutiert worden.