A5087969901- Advanced Chemical Physics Studies
- Molecular Junctions and Nanostructures
- History and advancements in chemistry
- Crystallography and molecular interactions
- Chemical Thermodynamics and Molecular Structure
- Spectroscopy and Quantum Chemical Studies
- Advanced Physical and Chemical Molecular Interactions
- Various Chemistry Research Topics
- Molecular spectroscopy and chirality
- Surface Chemistry and Catalysis
- Inorganic and Organometallic Chemistry
- Molecular Spectroscopy and Structure
- Photochemistry and Electron Transfer Studies
- Nonlinear Optical Materials Research
- Inorganic Fluorides and Related Compounds
- Spectroscopy and Laser Applications
- Atmospheric Ozone and Climate
- Mathematical functions and polynomials
- Magnetism in coordination complexes
- Free Radicals and Antioxidants
- Atomic and Molecular Physics
- Catalysis and Oxidation Reactions
- X-ray Diffraction in Crystallography
- Cyclopropane Reaction Mechanisms
- CO2 Reduction Techniques and Catalysts
Iowa State University
2015-2025
Ames National Laboratory
2015-2025
University of Siegen
2013
Tsinghua University
2013
Pacific Northwest National Laboratory
2013
United States Department of Energy
1990-2009
John Wiley & Sons (United States)
1976-2009
Texas A&M University at Galveston
1989
Uppsala University
1967-1982
University of Bonn
1975
A discussion of many the recently implemented features GAMESS (General Atomic and Molecular Electronic Structure System) LibCChem (the C++ CPU/GPU library associated with GAMESS) is presented. These include fragmentation methods such as fragment molecular orbital, effective potential orbital methods, hybrid MPI/OpenMP approaches to Hartree-Fock, resolution identity second order perturbation theory. Many new coupled cluster theory have been in GAMESS, multiple levels density functional/tight...
The quantum mechanical wave functions of molecules are discussed. An attempt is made to effect a simultaneous regional and physical partitioning the molecular density, pair energy, in such way that meaningful concepts can be associated with density energy fragments thus formed. origin chemical binding interpreted terms formulated process. (T.F.H.)
The topographies of two potential energy surfaces are examined in the vicinity their intersection. A brief account basic theory is given and possible surface types discussed explicitly. Two main patterns found. One these (‘‘peaked’’) has character a tilted double cone that lower (upper) decreases (increases) all directions from intersection which point where an infinite number, fact, orthogonal trajectories emanate. other pattern (‘‘sloped’’) results when both monotonically sloped touch each...
Optimal starting points for expanding molecular orbitals in terms of atomic are the self-consistent-field free atoms and accurate information about latter is essential construction effective AO bases calculations. For expansions SCF Gaussian primitives, which particular interest applications polyatomic quantum chemistry, previous has been limited accuracy. In present investigation a simple procedure given finding primitives to arbitrarily high The method furthermore opens first avenue so far...
The free-electron model for conjugated systems is consistently developed as the limiting case of a three-dimensional quantum-mechanical treatment π electrons in such systems. Joint conditions (for branching points) and boundary free end are derived hermiticity Hamiltonian shown. A matrix formulation theory established which makes application to large feasible, at same time leads close analogy with LCAO (LCAO MO considering only nearest neighbor interactions). Quantities analogous quantities...
Abstract A novel approach is developed for optimizing molecular orbitals within the context of a multiconfiguration self‐consistent‐field problem. The MCSCF wave function determined through sequence eigenvalue problems in space and single‐excitation space. They are used to iteratively improve natural orbitals, which turn related, by successively improved transformations, orbitals. mathematical arising out this general concept solved computational implementation discussed. In many...
Using a recently proposed procedure, the localized molecular orbitals are determined for minimal-basis-set LCAO—SCF wavefunctions of molecules LiH, BH, NH, FH, Li2, B2, Be2, N2, F2, CO, BF, LiF. In all cases, well-defined inner-shell, lone-pair, and bond found. They exhibit considerable degree transferability between different molecules, s-p hybridization varies regularly across periodic table. some cases deviate from accepted intuition; in exact determination intrasymmetry localization is...
The origin of chemical binding is analyzed with the help variational reasoning for ground state hydrogen molecule–ion. bond-parallel component kinetic-energy integral shown to be critical term. effect electron sharing on this term such that variation process yields, at all internuclear distances, a lower energy molecule than separated atoms. This appears paradoxical in as much as, equilibrium distance, potential part negative and kinetic positive. paradox resolved by showing actual values...
The problem of the two-center hybrid integrals is solved in a general way for Slater-type atomic orbitals with integral effective quantum numbers. No other restrictions are placed upon numbers and nuclear charges. expressed linearly terms one type auxiliary functions. A method finding coefficients given, latter computed all cases involving 1 2. functions discussed detail, methods given their computation. treatment developed shown to be applicable also Coulomb one-electron integrals.
Abstract The direct dissociation of ethylene into two methylenes is studied along the least motion reaction path by means an ab initio multiconfiguration self‐consistent‐field ( MCSCF ) calculation. All eight configurations arising from those valence orbitals that form CC bonds, seven them singlet coupled and one triplet coupled, are taken account. HCH bond angle optimized entire path. Separate optimizations carried through for lowest states 1 A g symmetry. σ 2 π ground state dissociates 3 B...
The relation between the orbital energies and total SCF energy of a molecule is discussed.(AIP)
A comparative study is made of the LCAO MO model (including overlap) and FE model. Energies electronic distributions are examined concepts ``atom population'' ``bond analyzed. close correspondence found to exist between two theories.
A theoretical calculation is presented for the main uv transitions of polyacenes, azulene, phenanthrene, isomers naphthacene and peri-condensed systems pyrene coronene. configuration interaction treatment, based on antisymmetrized products free-electron molecular orbitals, carried out, using methods developed this purpose in previous paper. Transition energies, intensities polarizations compare well with experiment. Particular emphasis placed upon illuminating various factors influencing...
Bases of even-tempered Gaussian primitives are optimized with respect to all parameters in the molecules hydrogen, methane, acetylene, ethylene, ethane, methyl water, carbon monoxide, dioxide, formaldehyde, and suboxide. A method is introduced for constructing contracted atomic orbitals from molecular these molecules. Transferability optimal primitive bases between shown. Certain minimization schemes basis discussed which greatly reduce amount work involved optimizations.
The quantum-mechanical treatment is carried through for a set of electrons in homonuclear conjugated bond system arbitrary size, including electronic interaction and all overlap effects between neighbors. All framework contributions are obtained by explicit integration over the Hamiltonian, effect nonconjugated neighbor atoms differentiating different types (joint, nonjoints, etc.). Expressions given ground-state energy, ionization potential, electron affinity, electronegativity,...
An analysis based on the variation principle shows that in molecules H2+, H2, B2, C2, N2, O2, F2, covalent bonding is driven by attenuation of kinetic energy results from delocalization electronic wave function. For molecular geometries around equilibrium distance, two features function contribute to this delocalization: (i) Superposition atomic orbitals extends one atom or more atoms; (ii) intra-atomic contraction further increases inter-atomic delocalization. The lowering (perhaps...
The free-electron network model for conjugated systems is extended to include electronic interaction. wave functions are considered as molecular orbitals arising from an average one-electron potential, and a configuration interaction treatment with these MO's developed. integrals occurring in this procedure, particular the electron integrals, analyzed convenient method their computation FE suggested. integral evaluation requires certain semiempirical parameters which determined benzene spectrum.