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In the present work, we have analyzed the elastic scattering data of [sup.6]He+p at 25.6,38.6,40.9, and 71 MeV/A and [sup.8]He+p at 15.6, 25.6, 32.5, 66, and 72 MeV/A, using the microscopic local optical potential calculated within the framework of the Brueckner-Hartree-Fock (BHF) formalism. The calculation requires mainly two inputs: (1) the nucleon-nucleon (NN) interaction and (2) the nucleon distributions in target nuclei. In the present work, realistic internucleon (NN) potential from Argonne v18 (AV18) and the Urbana IX (UVIX) model of three-body forces with several nucleon density distributions are used for generating the nucleon-nucleus optical potential. We have used the exact method for calculating both the direct and the exchange parts of the spin-orbit potential. We confirm the earlier results that the spin-orbit potential for these neutron-rich nuclei is diffused and extended. Our results show that the different density distributions reproduce rather well the experimental differential cross sections for both isotopes, while the phenomenological density with a two-neutron halo gives satisfactory results for [sup.6]He-p analyzing power data. None of the densities used for [sup.8]He can reproduce the experimentally analyzed power data. Our analysis reveals that the calculated microscopic optical potentials, with and without three-body forces using the BHF approach, provide satisfactory agreement with the elastic scattering data for [sup.6,8]He+p. Key words: Brueckner-Hartree-Fock (BHF) formalism, nucleon-nucleon (NN) interaction, exotic nuclei, halo nuclei, nucleonnucleus scattering, 1. Introduction The development of sufficiently intense secondary radioactive nuclear beams produced through high-energy fragmentation of nuclei opened new and exciting prospects for investigating the microscopic structure of light nuclei [...]

The spectroscopic properties of poly (styrene-co-p-vinylbenzyl chloride) (poly (St-co-VBC)) were investigated by Fourier transform infrared spectroscopy and *H nuclear magnetic resonance spectroscopic techniques. The molecular geometry and vibrational frequencies of macroinitiator, poly (St-co-VBC), were calculated by using density functional theory (DFT) and Hartree-Fock (HF) methods with 6-31 G+ (d, p) as a basis set. Calculated theoretical values are shown to be in good agreement with that of experimental values. An excellent harmony between the two data sets was verified. Besides, the experimental data of macroinitiator were compared with experimental data of its corresponding monomers such as St and VBC. The dimer and trimer forms of macroinitiator are used as significant contributions for getting an accurate interpretation of the experimental frequencies of poly (St-co-VBC). The results revealed that the change from St and VBC to poly (St-co-VBC) should be characterized by the disappearance of the C[H.sub.2]=CH bonds of the vinyl group and the appearance of the aliphatic C-H and C[H.sub.2] bonds. The geometrical parameters, Mulliken atomic charges and frontier molecular orbitals energies were also calculated using the same theoretical methods. The chemical shifts were calculated by using the gauge-including atomic orbital method and all the theoretically predicted values were shown to be in good agreement with experimental values. Molecular orbital properties, molecular electrostatic potential, and the potential energy surface for the atom transfer radical polymerization (ATRP) of the macroinitiator were studied with DFT and HF calculations. The potential energy surface of the ATRP initiator is decided by their electronic effect and steric hindrance effect simultaneously. Key words: styrene, p-vinylbenzyl chloride (VBC), macroinitiator, vibrational spectra, DFT, MEP, FMOs, ATRP. Nous etudions les proprietes spectroscopiques du poly (p-chlorure de venylbenzyl-co-styrene) (poly (St-co-VBC)) a l'aide des techniques de spectroscopie infrarouge a transformee de Fourier et de spectroscopie de RMN sur 1H. La geometrie moleculaire et les frequences vibrationnelles du macro-amorceur poly (St-co-VBC) sont calculees a partir des methodes de la fonctionnelle de densite (MFD) et de Hartree-Fock (HF) dans un espace de base 6-31G+ (d, p). Les valeurs calculees sont en bon accord avec les valeurs experimentales. Nous constatons une excellente harmonie entre les deux. De plus, nous comparons les valeurs experimentales du macro-amorceur avec les valeurs experimentales de ses monomeres, St et VBC. Les formes dimere et trimere du macro-amorceur contribuent significativement a une description precise des frequences experimentales du poly (St-co- VBC). Les resultats montrent que le changement de St et VBO a poly (St-co-VBC) apparait etre caracterise par la disparition des liens C[H.sub.2]=CH du groupe vinyle et l'apparition des liens aliphatiques C-H et C[H.sub.2]. Les parametres geometriques, les charges atomiques de Mulliken et les energies FMO sont calcules par les memes methodes theoriques. Les deplacements chimiques sont calcules en utilisant la methode des orbitales atomiques incluant les effets de jauge et nous montrons que toutes les valeurs theoriques sont en bon accord avec les valeurs experimentales. De plus, les proprietes des orbitales moleculaires, le potentiel electrostatique moleculaire et l'analyse des surfaces d'energie potentielle pour l'ATRP du macro-amorceur sont etudies par calculs MFD et HF et la surface d'energie potentielle de l'amorceur ATFP est fixee simultanement par leur effet electronique et leur encombrement sterique. [Traduit par la Redaction] Mots-cles : styrene, p-chlorure de venylbenzyl (VBC), macro-amorceur, spectres de vibration, DFT, MEP, FMOs, ATRP. PACS Nos.: 31.15.A, 31.15.ae, 31.15.at, 31.15.E-, 33.20.Tp., 1. Introduction Polymerization reactions involving a macroinitiator have aroused great interest because of the wide possibilities for the preparation of new polymeric materials. A popular and important controlled radical polymerization [...]

A comprehensive study of interaction potentials of the prototype silane dimer in terms of HF, MP2 and DFT methods is presented. The studies provide better understanding effects of the repulsion exponent, the binding energy, the equilibrium bond length, and the asymptotic behavior of the intermolecular potentials.

The complete active space self-consistent field (CASSCF) and complete active space second-order perturbation (CASPT2) methods and the multistate formulation of CASPT2 (MS-CASPT2) are used to calculate the ground and excited states of radical anions consisting of two [pi]-stacked nucleobases. The results have provided reasonable estimates for excess electron transfer (EET) energies, although the one-electron scheme cannot be applied to calculate electron affinities of nucleobases.

A generalized energy-based fragmentation (GEBF) approach is described for approximately predicting the ground-state energies and molecular properties of large molecules which are charged and polar molecules. The results have demonstrated that the approach could yield satisfactory ground-state energies, the dipole moments, and static polarizabilities for polar and charged molecules such as water clusters and proteins.

A study on the excited state properties of linear, planar, and spherical hydrogenated silicon nanostructures is conducted with use of a time-dependent Hartree-Fock (TDHF) approach with a semiempirical Hamiltonian. The calculated optical gaps decrease significantly from linear, planar, to spherical silicon structures, demonstrating that the optical gap is dimensionality dependent and hence it could be varied by solely managing the shape of the nanostructures.

A method that includes explicit electron-proton correlation directly into the nuclear-electronic orbital self-consistent-field framework is described. The nuclear-electronic orbital explicitly correlated Hartree-Fock (NEO-XCHF) method is computationally practical for many-electron systems since only a relatively small number of nuclei are treated quantum mechanically and only electron-proton correlation is treated explicitly.

Neutron diffraction data and crystal Hartree-Fock calculations are utilized to complement the multiple modeling of X-ray diffraction data. The experimental and theoretical evidences prove that the dipole enhancement for NMR in crystal is not at all close to the one previously reported, but is only on the order of 30-40% (~2.5D).

A study was conducted theoretically for the organometallic compound (NBu(sub 4)(sub 2) [Au(3,5-C(sub 6)F(sub 3)Cl(sub 2))(sub 2) Ag(sub 4)(cF(sub 3)CO(sub 2)(sub 5)], whose dianionic part displays a AuAg(sub 4) square pyramidal arrangement based on closed-shell Au(I)...Ag(I) interactions between two monoanionic fragments. The modelsystem [AuPh(sub 2)](super -)...[Ag(sub 4(CO(sub 2)H)(sub 5)](super -) (C1) was choosen from DFT results as an appropriate model for the study of the interactions.

A topological study of the Laplacian of the electronic density using a 6-311++G** basis set, at Hartree-Fock and second order Moller-Plesset levels of theory, for the carbocations 2-C-n-butonium generated upon the insertion of a proton into the secondary C-C bond during the protonation of n-butane. The sensitivity of some parameters derived from this topological analysis to the correlation effect of core electrons and subtle effects related to hyperconjugative interactions are shown.

The effects of n water molecules (n=1, 2, 3) on the conformational potential energy surface (PES) of acetylcholine (ACh) and acetylthiocholine (ATCh) using both the effective fragment potential method and fully ab initio calculations at a higher level is studied. The results demonstrate that the Hartree-Fock (HF) based EFP1 method can well represent the fully ab initio HF method.

The change in polyene bond lengths with distance from the polyacene and the modification of the HOMO-LUMO energy gap brought about by chemisorption of the polyene on some polyacenes is presented. The conclusion states that the dispersion interactions would play a role in the interaction between planar conjugated systems.

The influence of different alkali metal ions on the activity of Pt-ETS-10 in n-hexane aromatization is reported. The results of ab initio Hartree-Fock calculations on model clusters representing the Pt(active) site, molecular sieve with cations, Pt-M-molecular sieve, benzene, and H2S adsorbed over Pt-molecular sieve are presented.

The improved generator coordinate Hartree Fock method is used to generate Gaussian basis sets for lowlying excited states of neutral atoms from He (Z = 2) to Kr (Z = 36). Then, excitation energies and orbital energies of the outermost orbitals of each symmetry are calculated and compared with the corresponding values obtained with numerical Hartree-Fock calculations. Besides this, the basis sets for Be ([sup.3]P) and F ([sup.2]P) are contracted by a standard procedure and, then, enriched with polarization functions. From these basis sets, total energies, dissociation energy, and bond length for BeF are calculated and compared with results obtained with other basis sets and with experimental values. The sets for He-Kr are useful in constructing basis sets for molecular calculations. Key words: improved generator coordinate Hartree-Fock method, Gaussian basis sets, low-lying excited states, neutral atoms.

The Hartree-Fock method is used to calculate the reaction path for the catalytic conversion of adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP) by the enzyme mammalian adenylyl cyclase. It is shown that a reactive native structure of ATP bound in the active site of adenylyl cyclase can be constructed from an inhibitor X-ray structure.

The ground state spin arrangement based on the Huckel consideration by the Longuet-Higgins rule and simple valence bond approach is estimated. The estimates are compared with those by ab initio Hartree-Fock calculations and all of them elucidate the fact that the different heteroatom arrangements in the pi system cause the different spin-stable states of the singlet and the triplet.

The reaction mechanism of ribonuclease A and cytidyl-3',5'-adenosine and the geometry of the active site is optimized using the Hartree-Fock method and ab initio study. The refined conformations reveal an interesting hydrogen-bonding network that allows the prediction of the conformation of the active site in the initial step of the reaction mechanism.

The first principles quantum mechanical techniques are applied to the study of periodic models of four silica polymorphs containing different proportions of germanium as a substitutional species. Computations are performed using both the Hartree-Fock approximation and the gradient corrected density functional PWGGA technique.

Possible molecular conformations in peptide nanorings and nanotubes were theoretically investigated by a mathematical conformation analysis as well as ab inito Hartree-Fock calculations. The replacement by the appropriate residues is furthermore predicted to intrude additional levels in the energy gap and to form the frontier states localized at the side chains.

Hybrid density functional methods and a post-Hartree-Fock approach are used to investigate the magnetic behavior of the oxo-bridged Cu(II) dinuclear complexes. Both methods confirm the strong ferromagnetic coupling predicted for such complexes at geometries close to the energy minimum.

Calculations performed to study two vertical adsorption modes for H2S adsorption on x/MoS2 catalysts modeled by XMo2S10H6 (X= Zn, Cu, Ni, Co) clusters, via ab initio Hartree-Fock and pseudopotential approaches are reported. Results revealed that the adsorption energy depends on the metal promoter and on the electronic state of Mo2S10H6 moiety that determine the electron distribution of the X atom.

Byline: R. Bochicchio (1), L. Lain (2), A. Torre (2), R. Ponec (3) Keywords: population analysis; multicenter bonds Abstract: In this work we present the formulation of a topological population analysis derived from reduced density matrices of arbitrary order. We describe the construction of a mathematical framework which is suitable for handling any number of physical atomic regions. The procedure provides appropriate tools for enabling the detection and direct localization of multicenter bondings in molecules. Author Affiliation: (1) Dept. Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria 1428, Buenos Aires, Argentina (2) Dept. Quimica Fisica, Facultad de Ciencias, Universidad del Pais Vasco, Apdo. 644, E-48080, Bilbao, Spain (3) Institute of Chemical Process Fundamentals, Czech Academy of Sciences, Suchdol 2, Prague 6, 16502, Czech Republic Article History: Registration Date: 08/10/2004

The structural and electronic properties of C36 molecules are examined with two most possible geometries, which are studied using the Hartree-Fock (HF) theory, density functional theory (DFT) with the local density approximation (LDA). The results show that the ground state of the D(sub 6h) isomer strongly depends on the computational methods.

Byline: L.M. GaggeroaSager (1) Abstract: We present the exchange and correlation potential calculated analytically as a function of the Hartree potential. We arrived at this expression by using the Thomas--Fermi approximation. This is an alternative way of calculating the exchange and correlation potential which can be very efficient. Author Affiliation: (1) Escuela de Fisica, Universidad Autonoma de Zacatecas, Zacatecas, 98068, ZAC, Mexico Article History: Registration Date: 14/10/2004

Byline: Mario Piris (1) Abstract: The basic ideas of the Improved Bardeen--Cooper--Schrieffer (IBCS) approach to the firsta and secondaorder Reduced Density Matrices (1a and 2aRDM) are briefly reviewed. The molecular orbital occupations \ [rho] .sub.q \ are expressed by means of new quantities \ [gamma] .sub.q \ , which, satisfying a trigonometric relation, guarantee the nonaidempontent condition. Thus, a variational method is introduced to determine \ [rho] .sub.q \ , involving only an unconstrained minimization which may be performed using a conjugate gradient technique. A new effective Hamiltonian V which is composed of the Coulomb, exchange and exchangeatime inversion operators is also presented. It leads exactly to equations of Hartree--Fock type, however, the electronic field includes now an arbitrary number of orbitals and fractional occupation numbers. Accordingly, a generalized selfaconsistentafield method is proposed: the iterative procedure is repeated until convergence is reached for the actual density matrix. Author Affiliation: (1) Instituto Superior de Ciencias y Tecnologi a Nucleares, Ave. Salvador Allende y Luaces, La Habana, 10600, Cuba Article History: Registration Date: 14/10/2004

Ab initio calculations predict the existence of a dehydroprismane species more strained and pyramidalized than 1,2-didehydrocubene. Using Hartree-Fock, MP2-MP4 and CASSCF(2,2) packages, the study describes the optimized geometries, energies and vibrational frequencies of two olefinic prismane isomers. Prismene is shown to possess a double bond common to two four-membered rings while isoprismene has common double bonds between two three-membered rings. Isoprismene seems stable enough to be isolated by trapping. The prediction is supported by the successful trapping of an analogous isomer of chloroquadricyclene.

Substituent bulk tends to distort the central ring of 10-R-9-anthracenones. Molecular mechanics (MM2) calculations show that the molecule is flattest with H as R and, except for fluorine's bias for the pseudoequatorial position, all substituents tested prefer the pseudoaxis. Vibrational analysis shows that the planar structure is a true minimum on the potential energy surface at the 3-21G ab initio level. X-ray studies tend to confirm most MM2 predictions. Crystal packing, however, induces more planarity for the methyl and phenyl derivatives. These studies suggest that crystal 9-anthracenone itself is planar.

The effect of spin contamination is researched in single determinant wave function at the Hartree - Fock and density functional theory in studying adsorption on graphite. It is interesting to note that the spin contamination using unrestricted density functional theory was small, and the energetic information was almost unaffected.

The ab initio molecular orbital calculations of the diazomethanes and the isomeric diazirines show that the electronegativity and the conjugation properties of the substituents determine which isomer exhibits greater stability. The results have indicated that electronegative groups promote diazomethane destabilization while electropositive groups facilitate diazomethane stabilization. The HO, H2N, H2P and HS substituents favor twisted conformation geometries which are more stable than coplanar substituents. Moreover, the pi-acceptor stabilization property of substituted-diazomethane makes it more stable than diazirirines.

Classical spring model, density functional theory and ab initio Hartree-Fock plus Moller-Plesset correlation energy are used for studying the internal vibrations of the Li[(N[H.sub.3]).sub.4.sup.+] complex. The results have shown that the internal vibrations of Li[(N[H.sub.3]).sub.4.sup.+] complexes have resembled those of a tetrahedral object.

The angular integration of the exchange density is shown as a useful method for the partial visualization of its six-dimensional structure in three-dimensional space. The abundance of different spatial structures inherent in the radial exchange density has implied new capabilities for the orbital-independent interpretation of electronic structures in position space.

The nonlinear optical signal generated in phenol by three femtosecond pulses with wavevectors [k.sub.1], [k.sub.2] and [k.sub.3] in the phase-matching direction [k.sub.1] + [k.sub.2] - [k.sub.3] is simulated. The signal has vanished for uncorrelated electrons due to interference among quantum pathways, which is illustrated by the very different two-dimensional coherent spectroscopy (2DCS) signals.

The impact of carbon substitution patterns on the stability of [N.sub.18][C.sub.6][H.sub.6] isomers are studied using Hartree-Fock, density functional and perturbation theory. It is seen that carbon substitution in the nitrogen network results in stabilization of the cage but a decreases the detonation energy required for carbon substitution in the strong C-N bonds in [N.sub.18][C.sub.6][H.sub.6].

The charge-density-wave (CDW)-antiferromagnetic (AF) state phase transition is studied from the viewpoint of quantum AF fluctuations by using the resonating Hartree-Fock (Res-HF) method. The density has become asymptotically zero near the phase boundary, indicating the quantum decoherence or first order phase transition between the CDW and AF state.

A new density functional called M06-MF is presented which has full Hartree-Fock exchange and therefore eliminates self-exchange interactions at long range. The presented functional satisfies the uniform electron gas limit and it is better than the popular B3LYP functional for ground-electronic-state energetics.

The results obtained for the electronic levels and the relative mobility as a function of the doping density and the distance between delta wells by the means of Thomas-Fermi approximation are described. Hartree-Fock potential is obtained to compute the subband level structure and this expression is important for possible device application as well as for more elaborate self consistent calculations.

An efficient fragment-based approach for predicting the ground-state energies and structures of large molecules at the Hatree-Fock (HF) and post-HF levels is described. It is found that the molecular fractionation with conjugated caps scheme, if corrected by the interaction between non-neighboring fragments, can be used to predict the total energy of large molecules only from energy calculations on a series of small subsystems.

The Hartree-Fock and density functional theory methods that were used to study the high flexibility of the polyunsaturated fatty acid (PUFA) chain fragments are described. The similarities and differences of the two types of polymers can enable to understand the folding processes and membrane flexibility.

The functional dependence of excited-state geometries and normal modes calculated with time-dependent density functional theory (TDDFT) is investigated based on the vibronic structure calculations of the absorption spectra of large molecules. In most cases pure density functionals, which are computationally more efficient, provide less accurate spectra and their application is recommended to obtain estimates for the reliability of the theoretical predictions.

Hartree-Fock, electron correlation and semiempirical calculations were carried out on the DNA AT-specific intercalator tambjamine E in order to investigate the effect of protonation, side chins, electron correlation, and solvent on the inter-ring NCCN rotational barrier and relative planarity of the A and B rings. These properties relate to the flexibility of tambjamine and the ease by which it could adjust its inter-ring twist angle to adopt the propeller twist of DNA in order to form a nonclassical intercalation complex.

Four new REEF-HF parameter sets are developed for HF/6-31G(d) or HF/6-311+G(2d,p) energies and the corresponding NPA or mulliken charges. All parameter sets were developed and tested on the same molecular database set of 161 closed-shell neutral molecules composed of H, C, N, O, F, Si, S, and Cl atoms.

The permanent electric dipole moment of the isolated p-amino benzoic acid (PABA) molecule in the ground state along its principle axis is measured. The experimental value is compared to different calculations, and the accuracy of Hartree-Fock and density functional approaches to predict the electronic properties of Pi-conjugated systems is discussed.

The rapid estimation of basis set error and correlation energy from partial charges method is improved to make superfluous the explicit zero-point energy and thermal correction calculations. The new method is faster than the previous rapid estimation of basis set error and correlation energy from partial charges method, without losing the precision.

The rapid estimation of basis set error and correlation energy from partial charges (REBECEP) method is discussed which is improved further in several ways by introducing total energies derived from experimental enthalpies of formation instead of G3 energies in the fitting procedure. It was found the REBECEP method performed better for the 117 molecules with a moderate 6-31G(d) basis set than the B3LYP method with large 6-311+G(3df,2p) basis set.

The mechanisms of the double-proton transfer in the formamide-formamidine dimer, which resembled the model of the hydrogen bonding pattern in the adenine-thymine base pair was studied by means of ab initio post Hartree-Fock calculations. The results indicated that the gas-phase double-proton transfer possessed a concerted and asynchronous mechanism.

The energetics and the structure at the Hartree-Fock level is analyzed for the unsaturated system C36H16, its Si-doped analogue C32Si4H16 and several smaller, unsaturated fragments. The structural effects on the electronic distribution are described in terms of a localized orbital energy decomposition.

Formation of energetically favored, stable oligomer of [(Znq2)](sub 4) tetramer configuration in both the single crystal and the vacuum-deposited thin films of zinc(II) bis-(8-hydroxyquinoline) (Znq2) is reported. Analysis of electronic structure of [(Znq2)](sub 4) calculated by ab initio Hartree-Fock (HF) method reveals a localization and energy shift of high-lying occupied and low-lying unoccupied states of symmetry related ligands located on opposite sides of the supramolecular structure resulting in a dipole moment for [(Znq2)](sub 4) tetramer close to zero.

The screening and strain effects on the ground-state energy of the strained-layers semiconductor quantum wells forming a quasi-two-dimensional electron-hole plasma within the screened Hartree-Fock approximation are discussed. The screening plays an important role in determining the ground-state energy and the renormalization of the single-particle energies.

The results of an ab initio post-Hartree--Fock study of the protonation of all nucleic acid bases are described. The findings indicate that the rare tautomers make up a significant portion of the gas-phase equilibrium mixture.