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Harmonic Vibrational Frequencies (harmonic + vibrational_frequency)
Selected AbstractsMechanisms and kinetics for preparing carbohydrazide by reacting dimethyl carbonate with hydrazine: A theoretical studyINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2008Jianguo Zhang Abstract The mechanism and kinetic modeling for preparing carbohydrazide from dimethyl carbonate and hydrazine has been declared. The geometries of all the stationary points (reactants, intermediates, transition states, and products) are optimized by using the B3LYP method with the cc-pVDZ basis set, and the harmonic vibrational frequencies as well as infrared intensities are predicted with the same method. The minimum-energy paths are obtained by using the intrinsic reaction coordinate (IRC) theory at the B3LYP/cc-pVDZ level of theory with the step length 0.02 (amu)1/2·bohr. The rate constants are evaluated by using the TST, TST/Eckart, and RRKM (T)/Eckart methods. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Structures and properties of the hydrides of light elementsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2002Garry T. Smith Abstract Basic geometric and other properties for a number of neutral holovalent hydrides of light elements (M = Li , F)(MHn) are discussed. Their molecular geometries, energies, and vibrational frequencies have been determined from ab initio calculations of benchmark quality. We calculated harmonic vibrational frequencies, zero point vibrational energies, and atomization energies for the deuterides, tritiides, and combinations of them for these light elements. These isotopomers are of great interest for thermonuclear applications because they are often used as thermonuclear fuels or components of such fuels. In fact, only for these substances thermonuclear energy gain exceeds (at some densities and temperatures) the bremsstrahlung loss and other high-temperature losses, i.e., thermonuclear burn-up is possible. The vibrational frequencies are useful in determining the composition of mixed samples by means of spectroscopy. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] Development of new pseudopotential methods: Improved model core potentials for the first-row transition metalsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2003Christopher C. Lovallo Abstract We have recently developed new nonrelativistic and scalar-relativistic pseudopotentials for the first-row transition metal and several main-group elements. These improved Model Core Potentials were tested on a variety of transition metal complexes to determine their accuracy in reproducing electronic structures, bond lengths, and harmonic vibrational frequencies with respect to both all-electron reference data as well as experimental data. The new potentials are also compared with the previous model core potentials available for the first-row transition metals. The new potentials do a superior job at reproducing atomic data, reproduce molecular data as well as the previous version, and in conjunction with new main-group pseudopotentials that have L-shell structure of the valence basis set, they are slightly faster. © 2003 Wiley Periodicals, Inc. J Comput Chem 9: 1009,1015, 2003 [source] On the stability of non-conventional ,-complexes between Ni+ and toluene, phenyl-silane and phenyl-germane,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8-9 2006Inés Corral Abstract The complexes between Ni+ and toluene, phenylsilane, and phenylgermane were investigated through the use of high-level density functional theory (DFT) methods. Both harmonic vibrational frequencies and optimized geometries were obtained at the B3LYP/6-311G(d,p) and B3LYP/6-311+G(2df,2p) levels of theory. These results show that at the highest level considered in this work, and in contrast with what was found before for Cu+, the complexes in which Ni+ interacts specifically with only one pair of carbon atoms of the aromatic ring collapse to theconventional ,-complexes. However, similarly to Cu+, non-conventional complex in which the metal ion interacts with the ortho carbon of the aromatic ring and with one of the hydrogen atoms of the XH3 (X,=,Si, Ge) substituent group, through a typical agostic-type interaction are very stable. Nevertheless, whereas for Cu+ these agostic-type complexes are not only the global minima of the potential energy surface but the dominant species in the gas phase, for Ni+ they are slightly less stable than the conventional ,-complexes. Agostic-type complexes exhibit infrared spectra that are markedly different from those of the conventional ,-complexes, and therefore they could be easily identified using this spectroscopic technique. Copyright © 2006 John Wiley & Sons, Ltd. [source] On the Importance of CP-corrected Gradient Optimization in the Study of Hydrogen Bonded SystemsCHINESE JOURNAL OF CHEMISTRY, Issue 12 2003Wei-Zhou Wang Abstract Geometries, harmonic vibrational frequencies and interaction energies of the water-hydrogen sulfide dimer, hydrogen fluoride dimer and glycine zwitterion-water dimer were determined by the counterpoise-corrected (CP-corrected) gradient optimization that explicitly corrects for the basis set superposition error (BSSE) and CP-uncorrected (normal) gradient optimization respectively at the B3LYP and MP2 levels of theory, employing the popular Pople's standard 6,31G(d), 6,31G(d, p) and 6,311 + + G(d, p) basis sets in order to assess the importance of CP-corrected gradient optimization in the study of hydrogen bonded systems. The normal optimization of these three H-bonded systems obtained using these popular basis sets all yielded erratic results, whereas use of CP-corrected gradient optimization led to consistent results with those from larger basis sets. So this CP receipt becomes useful and necessary to correctly describe large systems, where the use of small basis sets may be necessary. [source] | ||||||||||