Showing papers in "Chemical Physics Letters in 1992"

TL;DR: In this article, the Brueckner coupled-cluster (BCCD) method with single and double excitations from a closed-shell reference function (CCSD) and the corresponding quadratic configuration interaction method (QCISD) are formulated in terms of quantities which can be computed directly from the two-electron integrals in AO basis.

TL;DR: In this paper, the performance of a hybrid of density functional theory and Hartree-Fock theory, the B-LYP/HF procedure, has been examined with a variety of basis sets.

TL;DR: In this paper, a multireference Moller-Plesset method is derived for 2-configuration MCSCF wavefunctions in which only two electrons are correlated, and potential curves for H 2, HF and F 2 molecules agree well with the full or near-full CI results.

TL;DR: In this article, surface second harmonic generation was used to probe the silica/water interface and it was found that the water molecules near the interface are polarized by the interfacial electric field and are responsible for the observed second harmonic light.

TL;DR: In this article, a new discrete variable representation (DVR) is proposed where the eigenstates of one-dimensional reference Hamiltonians are used to obtain the DVR localized basis functions.

TL;DR: In this paper, an algorithm is presented for determining multi-dimensional reaction coordinates between two known conformers, which is suitable for the study of complex isomerization reactions, including allosteric transitions in proteins and more general conformational changes of macromolecules.

TL;DR: In this article, the Kohn-Sham selfconsistent equations for exchange-correlation functionals are formulated using a finite orbital basis expansion, which can be solved iteratively without evaluation of density Hessians.

TL;DR: In this paper, an individual gauge for atoms in molecules is presented for relatively accurate ab initio calculations of molecular magnetic response properties, where the magnetic susceptibility and nuclear magnetic shielding tensors can be expressed in terms of the induced current density as a sum of separately determined atomic contributions.

TL;DR: In this paper, a formula for calculating NMR chemical shifts at second-order many-body perturbation theory using the gauge-including atomic orbital method is presented and their implementation is discussed.

TL;DR: In this paper, the structure and properties of the four possible bridging hydroxyl groups in silicon-rich H-faujasite (zeolite Y) are studied by lattice-energy minimization carried out within the classical shell model.

TL;DR: In this paper, the authors used least-squares or maximum-likelihood procedures and the multinomial distribution to find out how many detected photons one needs to achieve a certain accuracy in the lifetime estimate.

TL;DR: In this paper, new forms of multireference Moller-Plesset perturbation theory are presented that are applicable to high-spin open-shell systems and results are reported for the energy difference between the 1 A 1 and 3 B 1 states of CH 2 and for the potential energy curve of the triplet ground state (3 Σ − g ) of O 2.

TL;DR: In this paper, the second order hyperpolarizability of p-nitroaniline (PNA) was determined for solvents of varying polarity using the electric field induced second harmonic generation experimental technique.

TL;DR: In this article, analytical gradient techniques have been used to compute the structure and some properties of the ground state of the HOO radical with extended basis sets for unrestricted Hartree-Fock (UHF) reference functions.

TL;DR: In this paper, a variational procedure to calculate singlet-triplet energy differences in diradical systems is described, which includes all the differential second-order contributions, based on the theory of effective Hamiltonians.

TL;DR: In this paper, the correlation energy of crystalline silicon is determined by means of increments obtained in ab initio calculations for localized SiSi bond orbitals and for pairs and triples of such bonds.

TL;DR: In this paper, the electronic properties of bucky tube modelled by a sheet of helical graphite cylinder named "grahelix" have been examined based on the one-dimensional tight-binding crystal orbital method in the framework of the Huckel approximation.

TL;DR: In this article, the concept of wave functions with linear r 12 terms is combined with the coupled-cluster Ansatz at the CCSD and CCST[T] (formerly CCS D+T(CSSD)) levels.

TL;DR: In this article, the harmonic frequencies of C6H6 and C6D6 were obtained using the MP2 method and a TZ2P+f basis set (288 basis functions).

TL;DR: In this article, X-ray photoemission spectral probes of endohedral lanthanum-fullerene complexes, La@C n, show that the central La atom is in a formal charge state close to +3, and has been effectively protected from reaction with water an oxygen by the enclosing fullerene cage.

TL;DR: The properties of the zwitterionic form of glycine (NH + 3 CH 2 COO − ) using ab initio molecular orbital theory have been computed in this paper, where a shallow minimum on the ZWitterion potential energy surface may be located with certain basis sets that do not contain p-type polarization functions on hydrogen.

TL;DR: The storage requirement for the J and K operators in the naN4 algorithm has been removed with the cost of an additional direct Fock matrix construction.

TL;DR: A preparative high-performance liquid chromatography was examined for the isolation of higher fullerenes from CS 2 extracts of the carbon soot produced by arc heating of graphite in inert atmosphere.

TL;DR: In this paper, a computational scheme is proposed for ab initio calculations of electronic spectra of molecular systems, which is based on the different effects that determine the excitation energies and properties of the excited states.

TL;DR: In this paper, the photoionization threshold region of C60 has been studied using single-photon ionization with synchrotron radiation and mass selection is realized with a time-of-flight mass spectrometer.

TL;DR: The theory of atoms in molecules demonstrates the existence of an intramolecular hydrogen bond between a methyl group and a negatively charged oxygen in the biomolecules creatine and its competitive inhibitor carbamoyl sarcosine as discussed by the authors.

TL;DR: In this article, a reformulation of reference interaction site model theory is proposed, which makes use of the formally correct asymptotic form of the correlations obtained from the one-center angular expansion technique.

TL;DR: In this article, the authors used the complete active space SCF method and second-order perturbation theory to study the nickel atom's energy in the presence of a single atom.

TL;DR: In this article, pure C 60 was deposited on optical substrates in vacuo and spectroscopically characterized, and a small linear absorption coefficient α = 6 cm −1 was measured at 1.064 μm.

TL;DR: In this article, the idea of using a good representation as the zeroth order description of a problem, which is widely used in perturbation theory and in basis set calculations, is extended to the path integral formulation of quantum mechanics by constructing improved Feynman propagators.