Hideo Sekino

We construct high-order derivative operators for smooth functions represented via discontinuous multiwavelet bases. The need for such operators arises in order to avoid artifacts when computing functionals involving high-order derivatives of solutions of integral equations. Previously high-order derivatives had to be formed by repeated application...

A two-step subdiffusion behavior of lateral movement of transmembrane proteins in plasma membranes has been observed by using single-molecule experiments. A nested double-compartment model where large compartments are divided into several smaller ones has been proposed in order to explain this observation. These compartments are considered to be de...

As a refinement of the fluid mosaic model for explaining cell membrane functions, membrane-skeleton fence model and anchored membrane protein picket model have been proposed according to the tracing experiment of a single molecule in plasma membrane. In addition, the experimental observation that the diffusive motion of a transmembrane protein in p...

In one-dimensional multiparticle Quantum Cellular Automaton (QCA), the approximation of the bosonic system by fermion (boson-fermion correspondence) can be derived in a rather simple and intriguing way, where the principle to impose zero-derivative boundary conditions of one-particle QCA is also analogously used in particle-exchange boundary condit...

Linear fractional map type (LFMT) nonlinear QCA (NLQCA), one of the simplest reversible NLQCA is studied analytically as well as numerically. Linear advection equation or Time Dependent Schrodinger Equation (TDSE) is obtained from the continuum limit of linear QCA. Similarly it is found that some nonlinear advection-diffusion equations including in...

A Monte Carlo (MC) study is performed to evaluate the surface tension $\gamma $ of spherical membranes that may be regarded as the models of the lipid layers. We use the canonical surface model defined on the self-avoiding triangulated lattices. The surface tension $\gamma $ is calculated by keeping the total surface area $A$ constant during the MC...

MADNESS (multiresolution adaptive numerical environment for scientific simulation) is a high-level software environment for solving integral and differential equations in many dimensions that uses adaptive and fast harmonic analysis methods with guaranteed precision based on multiresolution analysis and separated representations. Underpinning the n...

We for the first time performed a systematic evaluation of dynamic second hyperpolarizabilities corresponding to all the third-order Nonlinear Optical (NLO) processes using Time Dependent Density Functional Theory (TDDFT) with exchange functional corrected for long-range interaction. We develop a program system which quantitatively evaluate the fre...

Music sounds are analyzed using a 12 even-tempered wavelet based upon the variable-density perfect translation invariance complex discrete wavelet transform (VD-PTI-CDWT) which divides an octave frequency band into 12 filter banks of equivalent width. Music chords generated from different sound sources thus analyzed are represented as scalogram and...

Detrended fluctuation analysis (DFA) was originally developed for the evaluation of DNA sequence and interval for heart rate variability (HRV), but it is now used to obtain various biological information. In this study we perform DFA on artificially generated data where we already know the relationship between signal and the physical event causing...

Time evolution of quantum particles like electrons is described by time-dependent Schrödinger equation (TDSE). The TDSE is regarded as the diffusion equation of electrons with imaginary diffusion coefficients. And the TDSE is solved by quantum walk (QW) which is regarded as a quantum version of a classical random walk. The diffusion equation is sol...

Quantum chemistry program based on Multiresolution Multiwavelet (MRMW) basis set is much simpler and can be more efficient than the conventional one based on Gaussian basis set in molecular geometry optimization because the Hellmann Fynman Theorem (HFT) holds for the complete space which MRMW provides. It is numerically shown that large Gaussian ba...

A multiscale simulation of a hydrophobic polymer chain immersed in water including the supercooled region is presented. Solvent effects on the polymer conformation were taken into account via liquid–state density functional theory in which a free-energy functional model was constructed using a density response function of bulk water, determined fro...

We evaluate dynamic molecular polarizability at near-resonance region using multiresolution multiwavelet (MRMW) basis set. The results obtained by traditional Gaussian basis sets are compared against the MRMW one. For perpendicular component, d-aug functions seem to be necessary. Very large Gaussian basis sets beyond d-aug-cc-pvqz can provide the r...

We propose a solution method of Time Dependent Schr?dinger Equation (TDSE) and the advection equation by quantum walk/quantum cellular automaton with spatially or temporally variable parameters. Using numerical method, we establish the quantitative relation between the quantum walk with the space dependent parameters and the “Time Dependent Schr?di...

This paper presents a new type of surface models constructed on the basis of Finsler geometry. A Finsler metric is defined on the surface by using an underlying vector field, which represents an in-plane tilt order. According to the orientation of the vector field, the Finsler length becomes dependent on both position and direction on the surface,...

Time Dependent Schrödinger Equation (TDSE) with an initial Gaussian distribution, is solved by a discrete time/space Quantum Walk (QW) representing consecutive operations corresponding to a dot product of Pauli matrix and momentum operators. We call it as Schrödinge Walk (SW). Though an Hadamard Walk (HW) provides same dynamics of the probability d...

An algorithm to evaluate the response function on the space spanned by Multi-resolution Multi-wavelet (MRMW) basis functions is implemented in a new efficient quantum chemical program system. Dynamic electric dipole polarizability of a molecule is evaluated for a range of applied optical frequencies as a preliminary application of the implementatio...

Hydration effects on high-pressure unfolding of a hydrophobic polymer chain are investigated through a multiscale simulation based on density-functional theory. The results strongly suggest the following: a thermodynamic origin for high-pressure denaturation, i.e., the decrease in volume due to the unfolding can be explained by the formation of a s...

IntroductionNonlinear Optical Response TheoryLong-Range-Corrected Density Functional TheoryEvaluation of Hyperpolarizability for Long Conjugated SystemsConclusions References

Quantum fluid dynamics-equation is solved using Multiresolution Multiwavelet (MW) basis functions. When Cayley formalism is used for the time progression operator, stable solutions are obtained not only for classical fluid dynamics problems but also for quantum fluid dynamics problems. requires additional care in order to obtain stable solutions. W...

We solve the time-dependent Schrödinger equation (TDSE), time-dependent Hartree-Fock equations (TDHF), and time-dependent Density Functional Theory DFT(TDDFT) [Runge and Gross, Phys Rev Lett 1984, 52, 997] equations of general electronic/muonic systems using a multiresolution multiwavelet (MRMW) basis set. The stable solution of these timedependent...

Nonlinear response properties in Time-Dependent Hartree–Fock (TDHF) theory are analyzed by diagrammatic techniques and compared with the expression in propagator theory. The term that ensures that the quadratic response function is correct through first order in electron correlation emerges in the coupling term between lower order TDHF amplitudes a...

The theoretical background of the Nonlinear Optical (NLO) property evaluation and the problems of previous methods are briefly described. The pioneering effort for quantitative evaluation of the property in QTP is described. It was motivated by the success of the emerging technology for obtaining rigorous ab initio molecular quantum wave-functions...

The solutions of convection and diffusion equations are analyzed using Multiresolution Multiwavelet (MRMW) basis functions of multidimension including time. The distribution representing the solution reconstructed in non-standard form of the higher order MRMW reproduces the original solution in the multidimensional space much more efficiently than...

Classical wave-equation is solved using Multiresolution Multiwavelet (MW) basis functions in one- and two-dimensional space. The time progression operator is represented using Cayley formalism in order to avoid instability of the solution. Stable solutions are obtained for different initial conditions.

A thermodynamic analysis of high-temperature and low-pressure unfolding of proteins using a coarse-grained multiscale simulation combined with a liquid-state density-functional theory is presented. In this study, a hydrophobic polymer chain is employed as a probe molecule for investigating qualitative changes in a hydration free energy surface acti...

Hydrophobic effects on multivalent-salt-induced self-condensation of a single polyelectrolyte chain such as DNA are investigated through a multiscale coarse-grained simulation based on density functional theory. We show that the water-mediated hydrophobic effect that was enhanced by hydration of multivalent salts plays an essential role in self-con...

The polarizabilities, α, second-hyperpolarizabilities, γ, and γ scaling factors, c, of polyynes [i-(Pr)3 Si–(CC)n–Si i-(Pr)3, H–(CC)n–Si i-(Pr)3, H–(CC)n-Ph, and Ph–(CC)n–Ph: n = 1 to 8] end-capped with triisopropylsilane (i-(Pr)3 Si–; TIPS) and phenyl groups were calculated using HF and DFT using the recently developed LC-BOP and LCgau-BOP functio...

Relativistic many-body perturbation theory calculations have been performed on the ground state of Ne atom. The reference state of the single configuration Dirac–Fock wave function was computed using an expansion of Gaussian basis functions. Second- and third-order correlation corrections were computed by systematically enlarging the basis set. The...

Density fluctuation effects on the conformation of a polymer chain in a supercritical solvent were investigated by performing a multiscale simulation based on the density-functional theory. We found (a) a universal swelling of the polymer chain near the critical point, irrespective of whether the polymer chain is solvophilic or solvophobic, and (b)...

The modified equation-of-motion coupled cluster approach of Sekino and Bartlett is extended to computations of the mixed electric-dipole/magnetic-dipole polarizability tensor associated with optical rotation in chiral systems. The approach – referred to here as a linearized equation-of-motion coupled cluster (EOM-CCL) method – is a compromise betwe...

We develop a dynamic equation solver using Caley algorithm with a multi-resolution multi-wavelet (MRMW) basis set. The method is applied for solving advection equation, the simplest yet most difficult equation for numerical solution.

Polarizabilities (alpha), second-hyperpolarizabilities (gamma), and the gamma scaling factors (c) of polyynes [H-(C[triple bond]C)(n)-H, n = 1-8] were evaluated using the long-range corrected (LC) density functional theory (DFT) and LC-DFT with a short-range Gaussian attenuation (LCgau), as well as high quality wavefunction methods. We show that th...

We describe the evaluation of response properties using multiresolution multiwavelet (MRMW) basis sets. The algorithm uses direct projection of the perturbed density operator onto the zeroth order density operator on the real space spanned by the MRMW basis set and is applied for evaluating the polarizability of small molecules using Hartree-Fock a...

The long-range correction (LC) for treating electron exchange in density functional theory, combined with the Becke-Lee-Yang-Parr (BLYP) exchange-correlation functional, was used to determine (hyper)polarizabilities of polydiacetylene/polybutatriene oligomers. In comparison with coupled-cluster calculations including single and double excitations a...

A self-consistent density-functional theory (DFT) for homogeneous and inhomogeneous classical fluids is presented using the density-functional Taylor expansion of an effective density that is introduced to describe the intrinsic excess free-energy functional. The first-order density expansion of the effective density around the uniform bulk density...

The density dependence of the fluid structure and electrical resistivity of dense fluid hydrogen are studied along an isotherm of T=10(4) K using a density-functional theory for an electron-proton binary mixture. A metal-nonmetal (M-NM) transition is estimated to occur around the dimensionless density value of r(s)=2.19. The electrical resistivity...

A dynanically adaptive grid scheme is introduced for the representation of quantum wavefunctions by Multiresplution Multiwavelet (MRMW) basis. A restricted direct product of individual dimension is introduced for representing the Cayley operator and it proves to reduce drastically the computational time and storage space for high dimension problems...

NMR chemical shifts are evaluated by the Fragment Molecular Orbital (FMO) method. Several practical approximations for the method are tested for water oligomer and poly-chloroprene. The FMO method reproduces the value by the ab-initio method without approximation and the experimental values. The adjacent approximation in fragment pair correction is...

The behavior of a polymer chain immersed in a binary solvent mixture is investigated via a single-polymer simulation using an effective Hamiltonian, where the solvent effects are taken into account through a density-functional theory for polymer-solvent admixtures. The liquid-liquid phase separation of the binary solvent mixture is modeled as that...

The hydrophobic interaction that is characterized by a potential of mean force (PMF) between spherical apolar solutes immersed in the simple point charge (SPCE) model for water was studied using an interaction site model integral equation based on a density-functional theory for molecular fluids. For comparison with the PMFs for various size solute...

The electrical conductance through benzene-dithiolate (BDT) between gold electrodes is studied using ab initio Green's function method coupled with GAUSSIAN 03 [1]. To simulate break junction experiments of BDT [2], we consider the energetic stability of transient structures of the BDT junction and possibility of the fluctuation among several struc...

Polarizabilities and second hyperpolarizabilities of polyacetylene and a hydrogen chain are evaluated by density functional theory (DFT) using a hybrid generalized gradient approximation functional with correct long-range electron-electron interactions. The well known catastrophic overestimate of the hyperpolarizabilities for molecular systems of e...

The Fragment-Molecular-Orbital (FMO) method is an approximate quantum chemical method for huge systems like biological macromolecules and is known to provide not only an accurate total energy but also properties of the system with sufficient precision compared with conventional first principle methods. In the present study we report the spectroscop...

Thermodynamic properties in dense fluid hydrogen are studied by using a density-functional theory for electron-proton binary mixtures that is called quantal hypernetted-chain (QHNC) integral equation. A nonlocal approximation for the exchange-correlation potential in a finite-temperature Kohn-Sham equation is presented. Results obtained from the QH...

The conductance behavior of the stretching processes in the STM break junction experiments was studied taking account of the effects of the energetic stability of the junction composed of benzene-dithiolate (BDT) and two Au(111) surfaces using the first principles calculations. The expected value of conductance computed with the three kinds of proc...

We implemented an interaction site model integral equation for rigid molecules based on a density-functional theory where the molecular orientation is explicitly considered. In this implementation of the integral equation, multiple integral of the degree of freedom of the molecular orientation is performed using efficient quadrature methods, so tha...

Previously, we showed that bikunin, a Kunitz-type protease inhibitor, inhibits invasion and metastasis in several types of cancer cells possibly through suppression of upregulation of urokinase-type plasminogen activator (uPA) expression. Bikunin corresponds to a light chain of the inter-alpha inhibitor. To explore critical role of endogenous bikun...

For prediction of molecular property and elucidation of physical mechanism it is important to use molecular dynamics(MD) simulation. However, there is necessity for speeding up MD simulation because these simulations of large size molecules such as dendrimer expend huge calculation cost. For that purpose, it is most effective to improve the part fo...

We applied a simulation method [T. Sumi and H. Sekino, J. Chem. Phys. 122, 194910 (2005)] to an infinitely dilute polyelectrolyte immersed in one-component charged fluids in order to investigate salt effects on its collapse. In this model system, the degree of freedom of the counterion (or the coion) is considered using a density-functional theory...

The expression of syndecan-1 generally appears down-regulated in human cancers and experimental models, whereas transfectional expression of syndecan-1 in cancer cells has been shown to inhibit aspects of their malignant behavior. To clarify how reduced levels of syndecan-1 may confer enhanced invasiveness, we transfected human ovarian cancer cell...

An efficient and accurate electronic structure method for clusters of weakly interacting molecules has been proposed, on the basis of the pair-interaction method of Kitaura et al., and combined with density functional, many-body perturbation, coupled-cluster, equation-of-motion coupled-cluster, configuration-interaction singles, and time-dependent...

The long-range interaction in density functional theory (DFT) is corrected using a partition technique of the two-electron operator when applied in the equation of motion (EOM) on the first-order density matrix. While the correction produces a minor effect on the static polarizabilities of small molecules, it improves the overestimated Cauchy coeff...

The long-range correction (LC) scheme for the exchange functional of density-functional theory (DFT) was combined with the coupled-perturbed Kohn-Sham (CPKS) method to calculate nonlinear optical response properties. By using this LC-CPKS method, we calculated the hyperpolarizabilities of typical molecules and the dipole moments, polarizabilities,...

Endometriosis, a common disease among women of reproductive age, is characterized by the presence of endometrial-like tissue outside the uterus. TNF-alpha induces IL-8 production in endometriotic cells through nuclear factor-kappaB (NF-kappaB) activation. Thalidomide (Thal) inhibits inflammation by down-regulating the expression of proinflammatory...

We propose a simulation method for infinitely dilute polymer solutions. In this method, an effective Hamiltonian of the solvated polymer chain is introduced to eliminate the degree of freedom of the solvent particle. The effective Hamiltonian is coupled with the density-functional theory (DFT) that we have developed for a polymer-solvent pair corre...

An anomalous increase of positron annihilation rare caused by a decrease of the temperature has been observed in supercritical fluid He-4 along isochors by an experiment. By using a molecular simulation, we demonstrate the similar increase in supercritical fluid xenon at the temperature that is far away from the liquid-vapor phase transition. The p...

Conformational change of a solvophobic polymer along an isotherm slightly above critical temperature of solvent is studied by using a simulation with an effective Hamiltonian of the solvated polymer chain, where solvent effects are taken into account. We observe an expansion of the solvophobic polymer in the vicinity of the critical density. The an...

Lipopolysaccharide (LPS) is the primary mediator of gram-negative sepsis; it induces the production of macrophage-derived cytokines. It has been shown that bikunin, a Kunitz-type protease inhibitor, inhibits LPS-induced cytokine expression. To explore the role of bikunin, bikunin knockout (Bik(-/-)) mice were used for in vitro cytokine experiments...

We provided evidence previously that bikunin, a Kunitz-type protease inhibitor, can disrupt dimerization of CD44 proteins, which may result in suppression of receptor-mediated MAP kinase signaling. However, to what extent dimerization may alter ligand-induced signaling has not been documented. Given the recent recognition that some growth factor re...

The specific interaction between catabolite activator protein (CAP) and cyclic adenosine monophosphate (cAMP) was investigated using the fragment molecular orbital method based on density functional theory (FMO-DFT). One of the efficient tools of FMO-DFT is the analysis of effective pair interactions, which are the pairwise fragment interactions un...

Bikunin is a multifunctional glycoprotein, which mediates suppression of tumor cell invasion and metastasis. The measurement of bikunin levels in the tissue of patients with malignant diseases has been introduced as a new and simple diagnostic tool for the evaluation of prognosis. The high bikunin expression in ovarian cancer tissue would enable th...

Bikunin, a Kunitz-type protease inhibitor, exhibits anti-inflammatory activity in protection against cancer and inflammation. To investigate the molecular mechanism of this inhibition, we analyzed the effect of bikunin on tumor necrosis factor alpha (TNF-alpha) production in human peripheral mononuclear cells stimulated by lipopolysaccharide (LPS),...

We previously found that bikunin (bik), a Kunitz-type protease inhibitor, suppresses transforming growth factor-beta1 (TGF-beta1)-stimulated expression of urokinase-type plasminogen activator (uPA) in human ovarian cancer cells that lack endogenous bik. In the present study, we tried to elucidate the mechanism by which bik also inhibits plasminogen...

The net balance between urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor type-1 (PAI-1) has been implicated in tumor cell invasion and metastasis. To elucidate the mechanism of the transforming growth factor-beta1 (TGF-beta1)-dependent up-regulation of PAI-1 expression, we investigated which signaling pathway transduce...

The atomic parameters in consistent charge equilibration (CQEq) method were optimized to reproduce electrostatic potentials around the 20 standard amino acid molecules. The introduction of two atom types for hydrogen improves significantly partial charges on hydrogen atoms. Geometry optimizations of a crambin protein were performed using force fiel...

We have used a density-functional theory based on the interaction site model to predict the liquid-vapor coexistence curve of nitrogen fluid. The pressure and chemical potential were calculated from thermodynamic integrations. The different paths of thermodynamic integration provide slightly different predictions for the liquid-vapor coexistence cu...

In this paper, we propose a path integral influence functional from a solvent to determine a self-correlation function of a quantum particle in classical simple fluid. It is shown that the influence functional is related to a grand potential functional of the pure solvent under a three-dimensional external field arising from a classical isomorphic...

Fragment molecular orbital (FMO) method is one of the approximations for calculating electronic properties of huge molecules such as DNA and protein. The accuracy and computational cost of FMO calculations depend critically on the way of dividing a molecule into fragments. In this study, we investigated the electronic properties of four types of DN...

Fragment molecular orbital (FMO) method, which has been proposed and tested to investigate electronic properties of large molecular systems for Hartree–Fock theory, is combined with density functional theory (DFT) to include the electron correlation effect. The convergence acceleration technique with direct inversion iterative subspace method is im...

Dipole and quadrupole moments computed in the fragment molecular orbital (FMO) scheme reproduce the results from the full molecular orbital (MO) theory within a few percent error. It is also shown that the FMO molecular orbitals for creating the FMO density matrix of each fragment provide qualitatively correct information on the chemical active sit...

UTChem is a quantum chemistry software developed by Hirao’s group at the University of Tokyo. UTChem is a research product of our work to develop new and better theoretical methods in quantum chemistry.

By combining the consistent charge equilibration (CQEq) method with universal force field (UFF), we developed the CQEq with UFF (CUFF) method and confirmed its efficiency for investigating the hydrogen bonding of DNA base pairs. By using the new parameters together with reduced van der Waals radii for hydrogen atoms, the CUFF method was capable of...

The thermal isomerization reaction of cis-azobenzene to its trans isomer has been studied by direct molecular dynamics. The semiempirical PM3 method was used to calculate the force field, which was verified by density functional (PW91) calculations. The transition state for the reaction was searched by both methods. The trajectories were started fr...

To elucidate a common feature of OmpR family enhancing the transcription ability of RNA polymerase, we investigated structures and electronic properties of DNA binding sites of OmpR family by semiempirical molecular orbital (MO) calculations. The results clarify that the highest occupied MO is localized on the 2nd aspartic-acid existing near the DN...

In order to accurately describe the van der Waals interaction between rare-gas atoms by the density functional theory, we adjusted the exchange-functional developed by Perdew and Wang (PW). The van der Waals interactions of He, Ne, Ar and Kr dimers were investigated. The results clarified that the adjustment improves the overestimation of the inter...

To evaluate the accuracy of density functional theory (DFT) for describing van der Waals interaction between rare-gas atoms, we performed coupled-cluster theory restricted to single, double, and noniterative triple excitations [CCSD(T)], fourth-order perturbation theory including single, double, and quadruple substitutions [MP4(SDQ)], and several D...

Hydrothermal flames at 25MPa supercritical water environment were investigated using a 4800ml reaction tower, in which the sapphire windows were fitted for optical access. Down flowing hydrothermal flames were observed for oxidation of 2-propanol when the reactor was fed with inlet organic concentration higher than 2vol% and air ratio higher than 1...

To elucidate a common feature of OmpR family, we investigated stable structures and electronic properties of DNA binding sites of OmpR proteins by semi-empirical MO method. The results clarify that the HOMO is localized on the 2nd aspartic acid for almost all families. This amino acid exists near the backbone of DNA, when OmpR binds to DNA. Therefo...

To evaluate the accuracy of density functional theory (DFT) for describing van der Waals interaction, we performed CCSD(T), MP4(SDTQ) and several DFT calculations for the He dimer. The results clarified that (1) CCSD(T) and MP4(SDTQ) with an `adjusted' diffuse basis-set reproduce the experimental binding energy as well as the equilibrium distance,...

Continuous flames have been observed in Supercritical water oxidation (scWO) of isopropyl alcohol (IPA), using a vertical continuous reactor with sapphire windows and a mixing nozzle. Two types of continuous flame were confirmed: the one was long pale blue colored and the other was red short cone shaped, changing blue to red at around air ratio 2.0...

An efficient direct integral-driven algorithm for the random-phase approximation (RPA) is introduced using the equation of motion on a transition density matrix representing a "quasi particle". In the algorithm, several roots are obtained at the same time by solving a set of coupled equations that are projected on a space spanned by a set of error...

An efficient direct integral driven algorithm for the Random Phase Approximation (RPA) is implemented using a new integral package SPHERICA. The most time consuming RPA operations on error vectors are accomplished by a single call of the integral generation routine based on Accompanying Coordinate Expansion (ACE) method. The program with SPHERICA i...

SCWO characteristics are investigated for a vertical type, down stream continuous reactor system with mixing nozzle and sapphire windows. 2-propanol, hexane and biphenyl solution are used as fuel and air as oxidizer. 2-propanol is observed to be effective as makeup fuel to keep a stable autogenic SCWO reaction. Even for low air ratio as 1.1, high d...

We show that introducing pseudospectral (PS) methodology into local space approximation (LSA) treatments reduces the scaling with system size by a factor of N, N being a measure of size, at both Hartree-Fock and correlated levels. Efficient ways to organize Hartree-Fock calculations, avoiding storage of full and local space two-electron integrals,...

We analyze the evolution of first principle molecular theory in obtaining reliable values of molecular hyperpolarizabilities. Such quantities place severe demands on the capability of quantum chemistry, as large basis sets, frequency dependence, and high levels of electron correlation are all shown to be essential in obtaining observed, gas phase h...

Non-linear response properties evaluated by Time Dependent Hartree Fock (TDHF) theory is represented in a Sum-Over-State (SOS) formulation. The formalism is completely equivalent to that obtained by the original formulation of TDHF using perturbed density matrices if all intermediate, excited states are taken into consideration. Severely truncated...

Introducing frequency dependence in the equation-of-motion coupled-cluster method, we evaluate the optical Kerr effect for butadiene and ammonia. This permits a critical evaluation of dispersion estimates via the uncorrelated time-dependent Hartree-Fock theory. The percentage dispersions are similar for low frequencies, but not for larger values. W...

Minimum-energy structures of clusters of one sodium atom and as many as three water molecules have been calculated by combining the method of ab initio Monte Carlo simulated annealing with conventional optimization methods. 6-31G* basis sets have been employed, and each structure was optimized at the MP2 (frozen core) level of theory. © 1995 John W...

We present an efficient formalism for property evaluation using the Hartree–Fock‐density‐ functional‐theory method. The formalism uses the relaxed density concept for first‐order properties which allows us to compute many different components of a property as well as many different properties once we have solved a single set of linear equations spa...

Electron correlation effects to the four coupling mechanisms which contribute to the isotropic nuclear spin–spin coupling constant, the Fermi contact (FC), paramagnetic spin–orbit (PSO), spin‐dipole (SD), and diamagnetic spin–orbit (DSO) are studied using the equation of motion coupled‐cluster (EOM‐CC) method. The second‐order properties are expres...

The coupled cluster (CC) treatment of a second-order property is expressed, analytically, by a generalized sum over state formulation based upon the equation of motion CC intermediate state wavefunctions. The method is applied to calculate the Fermi contact contribution to the indirect spin-spin coupling constants (J) of several molecules; ethane,...

Zero-valent tris(2,2'-bipyridine) aluminium ([Al(bpy)3]) is formulated as tris(2,2'-bipyridine (1-)) aluminium (III): each bipyridine ligand traps an electron. The ground-state doublet (2E) is more stabilized than the ground-state quartet (4A1) by a contribution of vacant aluminium 3dpi orbitals. The filled ruthenium 4dpi orbitals also take part in...

We report a systematic study of the first and second hyperpolarizabilities of several small molecules at a consistent level of theory and basis sets. Coupled cluster (CC) methods for correlation, analytical high- order time dependent Hartree-Fock (TDHF) theory for dispersion effects, and polarizability-consistent basis sets give agreement to about...

A new formalism and algorithm is developed for solving the general-order time-dependent Hartree–Fock (TDHF) problem. It is shown that for any order a generalization of the TDHF equations can be derived where all lower-order solutions constitute a constant term. This makes it very easy to obtain high-order solutions. As the space required for the ma...

Frequency dependent second hyperpolarizabilities of N2 and the prototype organic molecule trans‐butadiene are reported using generalized time dependent Hartree–Fock (TDHF) theory for several frequencies of applied fields. A monotonic increase of the values (positive dispersion) is observed for every nonlinear optical process in a range of frequenci...