The insertion reactions of CH,, CHF, CF2, SiH2, SiHF, and SiF2 into hydrogen molecule have been investigated by ab initio molecular orbital methods. Reactants, loose clusters, transition structures, and products were optimized at HF/3-21G and HF/6-3 1G*. For each structure, relative energies have been calculated at MP4SDQ/6-3 lG* and vibrational frequencies at HF/3-21G. A dramatic increase in t...

We numerically compare the semiclassical "frozen Gaussian" Herman-Kluk propagator [Chem. Phys. 91, 27 (1984)] and the "thawed Gaussian" propagator put forward recently by Baranger et al. [J. Phys. A 34, 7227 (2001)] by studying the quantum dynamics in some nonlinear one-dimensional potentials. The reasons for the lack of long-time accuracy and norm conservation in the latter method are uncovere...

High-frequency (HF) communications is undergoing resurgence despite advances in long-range satellite communication systems. Defense agencies are using the HF spectrum for backup communications, as well as for spectrum surveillance applications. Spectrum management organizations are monitoring the HF spectrum to control and enforce licensing. These activities usually require systems capable of d...

A hybrid quantum mechanical/molecular mechanical (QM/MM) potential energy function with Hartree-Fock, density functional theory (DFT), and post-HF (RIMP2, MP2, CCSD) capability has been implemented in the CHARMM and Q-Chem software packages. In addition, we have modified CHARMM and Q-Chem to take advantage of the newly introduced replica path and the nudged elastic band methods, which are power...

in this paper we have focused on the dielectric constant effect between various solvents with theoretical modelin the biochemical process. thereby, aaa, uuu, aag and uuc triplex sequences have been optimized inwater, methanol, ethanol and dmso with proposed scrf model of theory. the solvation of biomolecules isimportant in molecular biology since numerous processes involve to interacting a prot...

polycyclic aromatic hydrocarbons (pahs) are a class of compounds consisting of more than twobenzene rings fused in a linear, angular, or clustered arrangement and do not contain hetero atomsor carry subsistent. pahs originate from various sources. they are primarily formed byincomplete combustion of carbon-containing fuels such as wood, coal, diesel, fat, or tobacco. thepresent study reports an...

The properties of row-orthogonal hyperspherical coordinates and their associated hamiltonians for triatomic and tetraatomic chemical reactions will be reviewed and recent advances for pentaatomic systems will be given. References 1. A. Kuppermann, in Advances in Molecular Vibrations and Collision Dynamics, J. Bowman, ed. (JAI, Greenwich, CT, 1994); Vol. 2B, pp 117-186 2. A. Kuppermann, J. Phys....

A combined density functional (DFT) and incremental post-Hartree-Fock (post-HF) approach, proven earlier to calculate He-surface potential energy surfaces [de Lara-Castells et al., J. Chem. Phys. 141, 151102 (2014)], is applied to describe the van der Waals dominated Ag2/graphene interaction. It extends the dispersionless density functional theory developed by Pernal et al. [Phys. Rev. Lett. 10...

Much recent research has been conducted in the area of Bayesian learning, particularly with regard to the optimization of hyper-parameters via Gaussian process regression [1, 2]. The methodologies rely chiefly on the method of maximizing the expected improvement of a score function with respect to adjustments in the hyper-parameters. In this work, we present a novel algorithm that exploits noti...