Analytic gradients for the combined sr-DFT/lr-MP2 method: application to weakly bound systems

The formalism for analytical gradients in short-range density functional schemes with long-range ab initio corrections (sr-DFT/lr-ab initio) is presented. On the density-functional side, both sr-LDA and sr-PBE are available, while on the ab initio side lr-HF and lr-MP2 are possible. Details of the implementation in the Molpro package are given. Results from test calculations using different basis sets on weakly bound systems of the HB6/04, DI6/04, CT7/04 and WI9/04 databases are presented.     

The application of Dewitt-Morette path integrals to general relativity

The formulation of path integrals in terms of pseudomeasures by Cecile DeWitt-Morette is extended to infinite-dimensional state-spaces and to the state spaces dual to nuclear spaces appropriate to second-quantisation. In both cases a distribution formulation is given to allow a subsequent extension to manifolds. It is shown that the resulting theory is correct in that it can give rise to a wave function on state space which obeys a Schrödinger equation in appropriate circumstances. The corresponding state manifolds for quantum gravity are then defined, and the conditions under which the theory extends to them are discussed. it is shown in an appendix that the Riemannian metric required by the theory exists on one of the types of state manifold for a wide class of cases.     

Analytic two-loop master integrals for tW production at hadron colliders: I

We present the analytic calculation of two-loop master integrals that are relevant for tW production at hadron colliders. We focus on the integral families with only one massive propagator. After selecting a canonical basis, the differential equations for the master integrals can be transformed into the d ln form. The boundaries are determined by simple direct integrations or regularity conditions at kinematic points without physical singularities. The analytical results in this work are expressed in terms of multiple polylogarithms, and have been checked via numerical computations.     

A simple tight-binding approach to topological superconductivity in monolayer MoS_2

Monolayer molybdenum disulfide(MoS_2) has a honeycomb crystal structure.Here,with considering the triangular sublattice of molybdenum atoms,a simple tight-binding Hamiltonian is introduced(derived) for studying the phase transition and topological superconductivity in MoS_2 under uniaxial strain.It is shown that spin-singlet p+ip wave phase is a topological superconducting phase with nonzero Chern numbers.When the chemical potential is greater(smaller) than the spin-orbit coupling(SOC) strength,the Chern number is equal to four(two) and otherwise it is equal to zero.Also,the results show that,if the superconductivity energy gap is smaller than the SOC strength and the chemical potential is greater than the SOC strength,the zero energy Majorana states exist.Finally,we show that the topological superconducting phase is preserved under uniaxial strain.     

LR-CAHSQC: an application of a Carr-Purcell-Meiboom-Gill-type sequence to heteronuclear multiple bond correlation spectroscopy

A new pulse sequence, long-range CPMG-adjusted heteronuclear single quantum coherence (LR-CAHSQC), is proposed for the determination of long-range JCH coupling constants from a long-range 1H-13C correlation experiment. The long-range heteronuclear coupling constants can be directly extracted from COSY-type antiphase peak patterns. The current approach utilizes CPMG-sequences for polarization transfer, and thus avoids the evolution of homonuclear JHH couplings, which normally may introduce abnormalities into the cross peak pattern. The differences between LR-CAHSQC and normal LR-HSQC are discussed.     

Two-color non-linear spectroscopy: application to NO2

In this paper, we report about an application of the two-color laser-induced thermal gratings technique in the visible region to the detection of nitrogen dioxide in mixtures of nitrogen and argon at total pressure ranging up to 1 bar. We have investigated the dependence of the signal on the gas mixture parameters (pressure, NO₂ concentration, collision partners) and on the laser properties (beams polarization, pulse energy, bandwidth) at various instants during the temporal evolution of the thermal grating. Comparison of experimental results and theoretical predictions is performed. Finally, the detectivity of 4 ppm was obtained at normal conditions of pressure (1 bar) and temperature (300 K).     

An iterative algorithm for computing aeroacoustic integrals with application to the analysis of free shear flow noise

An iterative algorithm is developed for the computation of aeroacoustic integrals in the time domain. It is specially designed for the generation of acoustic images, thus giving access to the wavefront pattern radiated by an unsteady flow when large size source fields are considered. It is based on an iterative selection of source-observer pairs involved in the radiation process at a given time-step. It is written as an advanced-time approach, allowing easy connection with flow simulation tools. Its efficiency is related to the fraction of an observer grid step that a sound-wave covers during one time step. Test computations were performed, showing the CPU-time to be 30 to 50 times smaller than with a classical non-iterative procedure. The algorithm is applied to compute the sound radiated by a spatially evolving mixing-layer flow: it is used to compute and visualize contributions to the acoustic field from the different terms obtained by a decomposition of the Lighthill source term.     

A tight-binding approach to the electronic structure of the silver halides—I: Silver chloride

In this paper we present a modified version of the tight-binding method for determining the electronic structure of the silver halides. The main advantage of this approach is that it enables the bandstructure of these materials to be derived for all energies adjacent to the band gap. This is achieved by including an s function into the tight-binding basis set of atomic orbitals. In addition to the basic simplicity of the conventional tight-binding method this approach allows the ionicity of the potentials to be determined empirically by fitting the experimental band-gap and incorporates into the bandstructure calculation s-p and s-d interactions which may well be important.The validity of the approach is examined for the case of silver chloride and good agreement is obtained with previous calculations.     

Analytic approach to confinement and monopoles in lattice SU (2)

We extend the approach of Banks, Myerson, and Kogut for the calculation of the Wilson loop in lattice U (1) to the non-abelian SU (2) group. The original degrees of freedom of the theory are integrated out, new degrees of freedom are introduced in several steps. The centre group enters automatically through the appearance of a field strength tensor , which takes on the values 0 or 1 only. It obeys a linear field equation with the loop current as source. This equation implies that is non vanishing on a two-dimensional surface bounded by the loop, and possibly on closed surfaces. The two-dimensional surfaces have a natural interpretation as strings moving in euclidean time. In four dimensions we recover the dual Abrikosov string of a type II superconductor, i.e. an electric string encircled by a magnetic current. In contrast to other types of monopoles found in the literature, the monopoles and the associated magnetic currents are present in every configuration. With some plausible, though not generally conclusive, arguments we are directly led to the area law for large loops. Received: 27 August 1999 / Revised version: 29 October 1999 / Published online: 21 December 1999     

An approach to polyatomic Franck-Condon integrals: Application to the photoelectron spectrum of water

An analytical method, based on harmonic oscillator expansions for each normal coordinate and the neglect of the Duschinsky A matrix, is presented for the prediction of Franck-Condon factors in polyatomic molecules from ab initio electronic wavefunctions. The method is tested against earlier theoretical results for H₂ and LiH and then applied to predict the vibrational structure for the first band of the photoelectron spectrum of water.     

Analytic Tools to Brane Technology in N = 2 Gauge Theories with Matter

Exact solutions to the low-energy effective action (LEEA) of the four-dimensional N = 2 supersymmetric gauge theories are known to be obtained either by quantum field theory methods from S-duality in the Seiberg-Witten approach, or by the Type-IIA superstring/M-Theory methods of brane technology. After a brief review of the standard field-theoretical results for the N = 2 gauge (Seiberg-Witten) LEEA, we consider a field-theoretical derivation of the exact hypermultiplet LEEA by using the N = 2 harmonic superspace methods. We illustrate our techniques on a number of explicit examples. Our main purpose, however, is to discuss the existing analytical (calculational) support for the alternative methods of brane technology. We summarize known exact solutions to the eleven-dimensional and ten-dimensional type-IIA supergravities, which describe classical configurations of intersecting BPS branes with eight supercharges relevant to the non-perturbative N = 2 gauge theory with fundamental hypermultiplet matter. The crucial role of the M-Theory in providing a classical resolution of singularities in the ten-dimensional (Type-IIA superstring) brane picture, as well as the N = 2 extended supersymmetry in four dimensions, are made manifest. The two approaches to a derivation of the exact N = 2 gauge theory LEEA are thus seen to be complementary to each other and mutually dependent.     

Adhesion at a heterophase interface: First-principles study of Mo(001)/MoSi2(001)

The bonding characteristics, interfacial energetics, and electronic structure associated with adhesion at the Mo-MoSi₂(001) heterophase interface are investigated using the first-principles, self-consistent local orbital method. We found both the adhesive energy and peak interfacial strength for the interface to be 10%-15% smaller than the respective values for cleavage along the (001) planes in crystalline Mo and MoSi₂. The equilibrium interlayer separation between Mo and MoSi₂ is found to lie between the interplanar spacings of crystalline Mo and MoSi₂. The interfacial adhesive bonding is attributable to the combination of a nearly uniform band of charge accumulation at the interface and directional charge accumulation between atoms across the interface. These first-principles calculations demonstrate that the universal-binding-energy relation can be extended to describe adhesion between dissimilar materials.     

Microwave spectrum of 2-nitrophenol: Structure of the hydrogen bond

The microwave spectra of 2-nitrophenol and three isotopic modifications, 2-nitrophenol-d, 2-nitrophenol-¹⁸O, and 2-nitrophenol-¹⁸O-d, have been observed and assigned. The molecule is planar with the inertia defect $\text{Δ}\text{= ?0.360 ± 0.006}\text{amu}\text{A}\text{?}{}^2$ for all species. Using Kraitchman's method for the hydrogen coordinates and the oxygen “b” coordinate and the double substitution method for the oxygen “a” coordinate, the position of the phenol group in the principal axis system, and hence the OH bond length has been determined. The phenol OH distance is 1.00 ± 0.02 Å. In contrast to previously studied 2-aminoethanol, no marked structural changes due to the strong hydrogen bond are observed, in keeping with the results for a similar system, salicyl aldehyde. In addition to the ground state, four excited vibrational states for the normal species have been assigned. These are attributed to the torsion of the nitro group.     

Angle-resolved photoelectron spectroscopy of intramolecular hydrogen bond systems: 2-chloroethanol and 2-bromoethanol

He(I) photoelectron angular distributions of typical intramolecular hydrogen bond systems, 2-chloroethanol and 2-bromoethanol, were measured. The intramolecular hydrogen bonds were found not to influence the photoelectron angular distributions for the halogen atom lone pair bands of these compounds. This result is useful for spectral band assignments.