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Three-center integrals over Gaussian orbital and Kohn-Sham (KS) basis sets are reviewed. An orbital basis function carries angular momentum about its atomic center. That angular momentum is created by solid harmonic differentiation with respect to the center of an s-type basis function. That differentiation can be brought outside any purely s-type integral, even nonlocal pseudopotential integrals. Thus the angular factors associated with angular momentum and differentiation with respect to atom position can be pulled outside loops over orbital and KS Gaussian exponents. Key words: Gaussian orbital, solid harmonics, molecular integrals, pseudopotential. On examine les integrales a trois centres sur des bases d'orbitales gaussiennes et de Kohn-Sham (KS). Une fonction de base (orbitale) presente un moment angulaire autour de son centre atomique. Ce moment angulaire est cree par derivation des harmoniques solides par rapport au centre d'une fonction de base de type s. Cette derivation peut etre sortie de toute integrale purement de type s, meme d'integrales portant sur des pseudopotentiels non locaux. Donc, les facteurs angulaires associes au moment angulaire et la derivation par rapport a la position de l'atome peuvent etre sortis de la boucle sur les exposants orbitalaires et KS gaussiens. [Traduit par la Redaction] Mots-cles: orbitale gaussienne, harmoniques solides, integrales moleculaires, pseudopotentiel., Introduction Sambe and Felton (SF) started the process of bringing density functional theory (DFT) to chemistry. In quantum chemistry, the molecular orbitals are expanded in a finite number of Gaussian [...]

The analytic derivative of the electrostatic interaction between far separated fragments is developed and a number of restricted Hartree-Fock (RHF) geometry optimizations are performed by using the fragment molecular orbital method (FMO) and ab initio methods. The [alpha]-helix, [beta]-turn and extended conformers of a 10-residue polyanaline are analyzed and the good FMO accuracy is established.

The analysis of orbital contributions to canonical molecular orbitals (CMOs) of six abbreviated azolium analogs of the carbanion was carried out to understand the unique function of sulfur by applying natural bond orbital (NBO) theory. The analysis has suggested the operation of an H-bonding scheme that leads to the formation of a cryptic C2 carbanion that is not accumulated and the shielding of the carbanion by the N4'-H hydrogen bond that is weakened by N1'-H deprotonation.

The energies of B-type transitions are associated similarly to energy differences between the lowest unoccupied molecular orbital (LUMO) and higher virtual MOs in the dication. The Koopmans-type of calculations has provided a satisfactory interpretation of most of the features in these spectra.

An analysis of the electron density is made through natural bond orbitals (NBO), natural steric analysis (NSA), and atoms in molecules (AIM) methods and through analysis of frontier molecular orbitals (MOs). NBO shows that all compounds present through-bond interactions, but only the conformers of [2.2]-metacyclophane present significant through-space interactions.

A report on highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) eigenvalues predicted by using the 11 density functional theory (DFT) is presented. The methods can be used to predict molecular orbital (MO) eigenvalues and also be applied for simulation of molecular electronics and for understanding charge transfer in photoexcitation and redox chemistry.

Time-resolved EPR (TEPR) spectroscopy is used to study the spin dynamics in a series of D-B-A molecules (D= phenothiazine (PTZ), B = p-phenylene ([Ph.sub.n]), n=1-5 and A = perylene-3,4:9,10-bis(dicarboximide) (PDI)). The spin-orbit-intersystem crossing (SO-ISC) mechanism is a result of direct charge recombination, which also requires the initial radical pair (RP) intermediate and depends strongly on the orientation of the molecular orbitals involved in the charge recombination as well as the magnitude of 2J.

Comparison of SCC-DFTB and NDDO-based semiempirical molecular orbital methods was carried out. It is seen that SCC-DFTB and the NDDO methods all produce MP2/cc-pVTZ molecular geometries with average errors bond lengths, bond angles and dihedral angles of only 0.01Angstrom, 1.5 degrees and 3 degrees.

A model molecular wire sensor is proposed that can detect zerovalent chromium by a strong increase in conductance, when included in a metal-molecule-metal junction. The analysis has shown that the nature and the energies of the molecular orbitals change drastically after the complex is formed, resulting in a significant increase in conductance.

DFT calculations are used to study the geometrical structures and electronic properties of silica nanowires with and without the presence of external electric field. The results have shown that the stability of silica nanowires increases with the wire length and diameter, the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbits (LUMO) energy gap is more sensitive to the wire diameter than to the wire length, and the nanowires would be subject to breakdown in the strong electric field, and the breakdown threshold increases remarkably with the wire diameter.

Natural resonance theory (NRT) and natural bond orbital (NBO) analysis are performed on a symmetrical and an unsymmetrical substituted squaraine in order to understand the structure, bonding and lowest energy transitions in unsymmetrical squaraines. The results have shown that there is no distinctive advantage in absorption characteristics in unsymmetrical squaraines over that of the symmetrical squaraines except that these squaraines have dipole moment in the ground state.

An analysis of reaction efficiency is described for the reactions of carbonaceous ions and molecules. The results have shown that the combination of experimental rate-coefficient measurements and computations of the condensed Fukui functions of frontier molecular orbitals and pyramidal angles of [pi] orbitals is useful for describing the reactive sites on fullerene carbon clusters in the gas phase.

An electronic dynamics method where the time dependence of an external oscillating electric field is the perturbing part of the Hamiltonian is described. Application of the electric field induces charge movement inside the molecule and electronic transitions between the molecular orbitals.

Several molecular descriptors based on topological approaches as well as on a more traditional orbital-based decomposition, used to assess relations with hydrogen bond strengths in a series of formic acid dimers and its sulfur derivatives. A study devoted to the description of hydrogen-bond interactions through the use of few molecular descriptors is performed.

The electronic structures of the bis(dithiolene) anions [M(mnt)(sub 2)](super n-) (M = Ni, Pd, Pt; mnt = 1,2-S(sub 2)C(sub 2)(CN)(sub 2); n = 0-2) were examined by a combination of photodetachment photoelectron spectroscopy (PES) and functional theory calculations. The combined experimental and theoretical data provide insight into the molecular orbital energy levels of [M(mnt)(sub 2)](super 2-) and the ground and excited states of [M(mnt)(sub 2)](super 1-) and [M(mnt)(sub 2)].

A combination of x-ray absorption spectroscopy (XAS) measurements and StoBe density functional theory (DFT) calculations are used to study the electronic structures of the ferrocene-labeled peptides Fc-Pro(sub n-)OBz (n = 1 - 4). Excellent agreement between the measured and the simulated data is observed in all cases, and the origin of all major spectral features is assigned.

The gas-phase interactions between a linear nonionic oligomer and various model compounds (cofactors) are investigated by using PM3 semiempirical molecular orbital theory. The bond lengths, bond angles, delocalized molecular orbitals (DLMOs), and electron densities for the poly(ethylene oxide) (PEO)/cofactor complexes are consistent with hydrogen bonds, but the number of intermolecular R-OH...O and R-CH...O bonds do not correlate with the enthalpy of association.

A method for expressing the wave function in terms of Lewis structures is proposed and tested on the allyl cation. This method gives results that are consistent with the breathing orbital valence bond (BOVB) calculations for the energy and with the natural resonance theory (NRT) analysis for the weights of the Lewis structures.

The chemical reactivity of the 5-1DB defects are assessed from the analyses of the frontier molecular orbitals (FMOS) and local density of states (LDOS) and the reaction of nitric oxides (NOs) with the 5-1DB defects on the single-walled carbon nanotube (SWCNT) is described. It is indicated that the 5-1DB defects on the SWCNT is chemically reactive and can be used as the active site for the functionalization of SWCNT.

The reaction profile of Claisen rearrangement of chorismate mutase is analyzed by all electron quantum chemical calculations using the fragment molecular orbital (FMo) method. The study reveals that the hydrogen bonds connecting the substrates as well as the positive charge on one of the substrates highly affect the electrostatic stabilization.

The description of analogies between the symmetries of the bonding molecular orbitals in octahedral cages involving p-orbital delocalization, such as B(sub 6)H(sub 6)(super 2-), and those in analogues coinage metal cages involving d-orbital delocalization. The magnetic properties reveal that the copper cages are likely to be most stable among coinage metal cages.

(Received 9 March 2005; accepted 23 September 2005) We explore a relation suggested by the united-atom and separated-atom limits between the one-electron Darwin and mass-velocity relativistic contributions to the ground state molecular orbital of [H.sup.+.sub.2].

The electronic origin of intermolecular (super 1h)J(A,H) and (super 2h)J(A,D) coupling is discussed by means of the (contributions from localized orbitals within the polarization propagator approach) CLOPPA-IPPP approach in several model complexes with D-H...A hydrogen bonds. It is found that the origin of these couplings is mainly due to the interaction between the acceptor sigma lone pair and vacant molecular orbitals localized in the D-H...A moiety, regardless of the donor and acceptor nuclei.

The potential energy hypersurfaces (PESs) of heptasulfer (S7) and of [LiS7](super +) are investigated by ab initio molecular orbital calculations at the G3X(MP2) level theory. It is shown that the S7 molecule like the related S6 and S8 species forms at least six isomers on the potential energy surface that are more stable than open-chain isomers.

The interactions of an H2O molecule with cluster models of fractured silica surfaces were studied by means of quantum mechanical calculations. The calculations suggested that when the silica is fractured in a vacuum homolytic cleavage is favored.

A quantum chemical study is conducted to assess changes in aromaticity along the T1 state Z/E-isomerization pathways of annulenyl-substituted olefins. The minimum on the T1 potential energy surface (PES) corresponds to the olefin structure with highest substituent aromaticity for olefins with annulenyl substituents.

Potential energy surfaces for the alkaline hydrolysis of sarin and O,S-dimethyl methylphosphonothiolate, a VX model compound, and the perhydrolysis of the latter are computed at the MP2/6-31+G(d)//mPW1K/MIDI level of theory. Excellent agreement with the experimental enthalpy of activation for alkaline hydrolysis of sarin was found.

A new computational scheme integrating multi-center ab initio molecular orbitals for determining total energy and normal vibration of large cluster systems is presented. The geometry parameters, the total energies, the relative energies, and the normal vibrations for four models of water cluster, the hydrated hydronium ion complex, and the transition state of proton transfer is calculated by the present method and are compared with those obtained by the full ab initio MO method.

The unimolecular decomposition of ethylene oxide and the oxiranyl radical is examined by molecular orbital calculations, Rice-Ramsperger-Kassel-Marcus (RRKM)/Master Equation analysis, and detailed kinetic modeling of ethylene oxide pyrolysis in a single pulse shock tube. It was found that the largest energy barrier to the decomposition of ethylene oxide lies in its initial isomerization to form acetaldehyde.

The diffusion of water in amorphous SiC (a-SiC) is studied using molecular orbital methods based on density functional theory to calculate the interaction energetics between the diffusant and the network. The results reveal that along its diffusion path through the SiC network the water molecule neither breaks up nor attaches itself to the SiC network and the energy barrier for diffusion depends mainly on the local SiC ring topology.

Ab initio molecular orbital calculations is employed to investigate the interactions between a set of basic substrate (B) with H(super +) and HF and the interaction between acids of varying strength (AH(super +)) with two bases, vinylamine and furan. The preferred site for protonation of the substrates appears to be determined primarily by the ability of the protonated species (BH(super +)) to delocalize the acquired positive charge.

Ab initio molecular orbital theory was employed to study base-catalyzed hydrogenation, to better understand and to rationalize the limitations of the catalytic reaction. A good balance between polarity and catalyst solubility is required in selecting the optimum solvent for the base-catalyzed hydrogenation reaction.

Current rectification by a Langmuir-Schaefer monolayer of a new molecule, fullerene-bis[4-diphenylamino-4'-(N-ethyl-N-2''-ethyl)amino-1,4-diphenyl-1,3-butadiene] malonate, sandwiched between two gold electrodes is reported. The rectification is ascribed to the asymmetric placement of the relevant molecular orbitals, with respect to the metallic electrodes.

Pd K-edge X-ray absorption near-edge spectroscopy (XANES) probes different molecular orbitals and consequently the charge distribution in a series of bidentate diphosphine ligands (PP) Pd coordinating moieties (XX) complexes. A full interpretation of the Pd K-edge XANES data is presented.

The study calculated the framework of PM3 molecular orbital approximation the thermodynamic function characteristics of the formation and geometrical structure of monomers, dimers, trimers, and tetramers of fluoroalkanols. It concluded that fluoroalkanol monomers posses a helical structure with an average backbone torsion angle equal to 162 degree, which implies optical activity of these molecules and the existence of two types of dimers, dimers with equal and opposite directions of helixes winding.

Kinetic experiments and high-level ab initio molecular orbital calculations were used to study the cumyl dithiobenzoate (CDB)-mediated reversible addition fragmentation chain-transfer (RAFT) polymerization of styrene at 30 degree Celsius. The kinetic data indicates the delayed onset of steady-state behavior.

A study was conducted on the structure, bonding, vibrational and electronic properties of small clusters of gallium oxide, Ga(sub m)O(sub n) (m, n =1,2) with a focus on the changes induced by the addition or removal of an electron from the neutral species. It was found that the addition of an electron introduced relatively larger structural changes than the removal of an electron from the neutral cluster.

The reaction cross sections of the collisionally activated process I(super -) + CH3Y -> products were measured using guided ion beam tandem mass spectrometry techniques. The reaction mechanisms were explored with the help of CCSD(T)/LanL2DZ and CCSD(T)/SDD molecular orbital calculations and phase space theory.

The aromaticity of the hydrosilver(I) and hydrogold(I) analogues of aromatic hydrocarbons is verified by a number of established criteria of aromaticity, such as structural, energetic, magnetic, and chemical criteria. The comprehensive study of the structural, energetic, spectroscopic, and bonding properties of the novel classes of inorganic compounds containing bonds that are characterized by a common ring-shaped electron density, more commonly seen in organic molecules, is presented.

An investigation was conducted on the photochemical reaction pathway of silacyclopropenylidene(c-C2H2Si) using the eight electrons in eight orbitals complete active space 6-311++G(3df,3pd) basis set. The difference in the photochemical cleavage sites was explained by the difference in the electronic nature of the Si excited state.

The electrochemical properties of 1,2, and 3 are rationalized by molecular orbital (MO) calculations using the density functional theory (DFT) method. Specifically, the molecular orbital (MO) calculation suggests that significant contribution of the metal cluster center to unoccupied molecular orbitals in 3, which is consistent with the experimental result of strong interfullerene electronic communication via the Rh6 metal cluster spacer.

The generalized hybrid orbital (GHO) approach is used to combine a quantum mechanical (QM) fragment described by the self-consistent-charge density-functional tight-binding (SCC-DFTB) method with a fragment described by molecular mechanics. The results indicate that the GHO treatment for combining SCC-DFTB with molecular mechanics is both theoretically robust and satisfactory for practical use.

The combined UPS and XPS study of Mg-PyPySPyPy interfaces shows the formation of two gap states for both metal-on-organic and organic-on-metal structures. The gap states are most consistently described as localized molecular orbitals, associated with the charge transfer complex.

A study using the two level ONIOM (B3LLYP/6-31G(d,p):PM3) and ONIOM (B3LYP/6-31G(d,p):HF/3-21G) methodology together with cluster model approximation is conducted to determine the adsorption of sarin (GB) and soman (GD) on the octahedral surface of dicksite. It is reported that polarization occurs due to adsorption and changes in the geometric parameters of the adsorbed molecules and also forms an attractive contact between the GB, GD and the surface of the dickite.

The study was conducted on the diagonal and off-diagonal tensor components of the first hyperpolarizability of a series of A-shaped molecules, which are compared by the means of ab initio and semiempirical molecular orbital calculations. The results show that the A-shaped molecules with DAD-or ADA-patterns gives quantum chemical calculations for the first hyperpolarizability.

Metal complex is significant for knowing its chemical reaction and its function as mediators in the reactions that take place photochemically to thoroughly understand the attitude of excited state of transition. The spin depth is importantly localized on the Pt atoms, which provide an idea about the capability of the triplet excited state to remove hydrogen and halogen atoms from organic substrates.

Byline: Gordon J. Miller (1), John G. Verkade (1) Keywords: Huckel MO theory; generator orbitals; spherical harmonics; fullerenes Abstract: The nearly spherical nature of small fullerene cages C.sub.N (N&lt 70) suggests that their [pi] molecular orbital (MO) energy diagrams should show a shell structure. Although group theoretical analysis of the Huckel-type energies for icosahedral and other highly symmetric cages confirms this assumption, this has not been established for fullerene cages in general. This work presents a simple computational algorithm based upon the canonical orthogonalization of generator orbitals (GOs) to analyze the [pi]-MO energy diagrams for any fullerene cage C.sub.N, and demonstrates the validity of a shell structure in these diagrams. Results are compared to simple central force (spherical) models for the calculations of [pi]-MO energies in fullerene cages. The GO approach provides a ready assignment of the [pi]-MOs to individual spherical harmonics and allows valuable interpretations of various physical phenomena. Author Affiliation: (1) Department of Chemistry, Iowa State University, Ames, IA, 50011, USA Article History: Registration Date: 08/10/2004

The novel fused Zn(II)porphyrin arrays (Tn, porphyrin tapes) have been investigated by steady-state and time-resolved spectroscopic measurements along with theoretical MO calculations. The overall relaxation dynamics of the porphyrin tapes show a systematic change as the number of porphyrin pigments increase in the array