In this series of studies, we systematically apply the analytical energy gradients of the direct symmetry-adapted cluster-configuration interaction singles and doubles nonvariational method to calculate the equilibrium geometries and vibrational frequencies of excited and ionized states of molecules. The harmonic vibrational frequencies were calculated using the second derivatives numerically c...

Ab initio electronic structure calculations on several low-lying valence states of B, have been carried out using correlation-consistent polarized valence double-zeta basis sets and completeactive-space self-consistent field treatments of electron correlation. Stable triangular structures, linear structures, and Jahn-Teller unstable structures are all observed. Equilibrium geometries, energies,...

In this paper, homotopy perturbation and modified Lindstedt-Poincare methods are employed for nonlinear free vibrational analysis of simply supported and double-clamped beams subjected to axial loads. Mid-plane stretching effect has also been accounted in the model. Galerkin's decomposition technique is implemented to convert the dimensionless equation of the motion to nonlinear ordinary differ...

the paper investigates into the vibrational characteristics of the truck chassis including the natural frequencies and mode shapes. truck chassis forms the structural backbone of a commercial vehicle. when the truck travels along the road, the truck chassis is excited by dynamic forces caused by the road roughness, engine, transmission and more. modal analysis using finite element method (fem) ...

the thermodynamic functions such as enthalpy (h), gibbs free energy (g) and entropy (s) ofpyrazole was theoretically studied at 5 different temperatures 25, 30, 35, 40 and 45°c by usinggussian o3, software. first, the structural optimization of isolated pyrazole was done in the gas phaseby appling the density functional theory (b3lyp) level with 3-21g, 6-31g and 6-31+g(d) basissets. moreover, v...

__________________ Abstract _____________________________________________________________________ The conformational stability, intramolecular H-bond strength, energy barriers, vibrational frequencies and gas-phase basicities of fourteen most stable conformers of ethanolamine in gas phase and in aqueous and carbon tetrachloride solutions have been investigated at B3LYP and MP2 level with 6-311+...

The infrared spectra of 1-methylthymine (1-MeT) in argon and nitrogen cryogenic matrices are presented, for the first time. The molecular structure, conformations, vibrational frequencies, infrared intensities and Raman scattering activities of 1-MeT have been calculated by the DFT(B3LYP), MP2 and HF methods using the D95V** basis set. The theoretically predicted intensity pattern of the IR and...

The structure and vibrational frequencies of styrene and trans-b-methyl styrene in the lowest three singlet states ~S0 , S1 , and S2! have been calculated using ab initio quantum chemical methods. The frequencies are compared with experimental data obtained in the bulk and in a supersonic jet. The calculation shows that in the ground state the molecules have a broad shallow potential as a funct...

Two-dimensional infrared spectroscopy is capable of following the transfer of vibrational energy between modes in real time. We develop a method to include vibrational relaxation in simulations of two-dimensional infrared spectra at finite temperature. The method takes into account the correlated fluctuations that occur in the frequencies of the vibrational states and in the coupling between th...

Molecular dynamics (MD) simulations of chloroform vapor and liquid at normal temperature and pressure and liquid under hydrostatic pressure are presented, giving bond lengths and vibrational frequencies as functions of pressure. The change in bond lengths between vapor and liquid at normal temperature and pressure is consistent with a pressure equivalent to the cohesive energy density (CED) of ...