Results 131 to 140 of about 38,282 (168)

Ab Initio Calculations of Metalloporphyrins

1982
Publisher Summary This chapter explores that the metalloporphyrins that are fascinating molecules to both the coordination chemist and the biologist. They appeal to the coordination chemist for several reasons: 1. their ability to incorporate a wide variety of metals, 2. their rich stereochemistry, 3. their variety of oxidation states, and 4.
A. Dedieu, M.-M. Rohmer, A. Veillard
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Ab initio calculations of the pyrophosphate hydrolysis reaction

Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1991
Ab initio quantum mechanical calculations were used to study the hydrolysis reaction H4P2O7 + H2O in equilibrium with 2H3PO4, as well as some molecular properties of the reactants and products. SCF calculations with several basis sets ranging from minimal to extended with polarization functions were used to look at the basis dependency of the reaction ...
H, Saint-Martin, I, Ortega-Blake, A, Leś, L, Adamowicz   +3 more
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Ab-Initio Calculation of the Optical Properties of Surfaces

physica status solidi (a), 1998
The recent development of computational methods using very large plane-wave basis sets, together with the large increase in computer performance, have now made it possible to compute the optical properties of real surfaces within a parameter-free approach.
ONIDA, GIOVANNI, DEL SOLE, RODOLFO, PALUMMO, MAURIZIA, PULCI, OLIVIA, Reining, L.   +4 more
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Benzooxirene. Ab initio calculations

Journal of Molecular Structure: THEOCHEM, 1996
Abstract Ab initio calculations have been performed on benzooxirene, the corresponding oxo carbene (“ketocarbene”), and the transition state linking the two. At the highest level used, QCISD(T)/6-31G ∗ //MP2(FULL)/6-1G ∗ with MP2(FULL)/ 6-31G ∗ zero point energy corrections, the relative energies of the oxirene, the transition state and the carbene
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MP2, DFT and ab initio calculations on thioxanthone

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2011
Density functional theory (DFT), HF and MP2 calculations have been carried out to investigate thioxanthone molecule using the standard 6-31+G(d,p) basis set. The results of MP2 calculations show a butterfly structure for thioxanthone. The calculated results show that the predicted geometry can well reproduce the structural parameters.
Alireza Salimi, Beni, Alireza Najafi, Chermahini, Hashem, Sharghi, Setareh Mirzaei, Monfared   +3 more
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Ab Initio Calculations on the Formation and Rearrangement of Spiropentane

The Journal of Physical Chemistry A, 2009
The formation of spiropentane, by addition of singlet (1A1) methylene to methylenecyclopropane, and the unimolecular reactions of spiropentane have all been studied computationally. Benchmark calculations on two key biradicals were conducted by the multireference Mukherjee's coupled-cluster (MkCC) method.
Barry K, Carpenter, Jiri, Pittner, Libor, Veis   +2 more
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Ab Initio Calculations on Bismuth Cluster Polycations

Chemistry - A European Journal, 2001
Ab initio calculations on bismuth polycationic species of the types Bi(n(n-2))+, Bi(n(n-4))+, and Bi(n(n-6))+ (n = 3 - 12) were performed at the Hartree-Fock and density functional theory levels in order to investigate their general properties and the applicability of Wade's rules on bismuth polycations. Some exceptions to Wade's rules were encountered,
A N, Kuznetsov, L, Kloo, M, Lindsjö, J, Rosdahl, H, Stoll   +4 more
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Ab-Initio Calculations of the Vibrational Properties of Nanostructures

2012
We study, via ab initio density functional theory (DFT), the vibrational properties of semiconductor colloidal nanostructures. The calculations are performed on the NEC Nehalem clusters at the High Performance Computing Center Stuttgart (HLRS). We find a relatively large blue shift of the longitudinal acoustic, transverse and longitudinal optical modes
Gabriel Bester, Peng Han
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Ab Initio Calculations of Clusters

2004
Both ab initio quantum chemistry and the investigation of atomic or molecular clusters are fields of active research nowadays. This contribution presents on one hand some advances in making programs efficient for calculations of large systems, on the other it shows some fruitful combinations of calculated and experimental results.
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Geometry optimization in ab initio SCF calculations

Journal of Molecular Structure: THEOCHEM, 1980
Abstract The floating orbital geometry optimization (FOGO) described previously is applied to H2O2, NH3, HNC, HNO, HNCO, and CH3OH. In the FOGO method we apply two analytically calculated energy gradients in a variable metric method. Some orbitals are no longer fixed on the corresponding nuclei, but their position is optimized simultaneously with the
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