1,720,997 research outputs found
MOLECULAR-DYNAMICS STUDIES ON ZEOLITES .6. TEMPERATURE-DEPENDENCE OF DIFFUSION OF METHANE IN SILICALITE
No full textAbstract: The effect of the temperature on the diffusion of methane in silicalite was studied by molecular dynamics both using a model where the vibrations of the zeolite framework are taken into account and keeping the framework fixed. Methane molecules were represented by Lennard-Jones particles. The diffusion coefficients were evaluated at four different temperatures in the range 150-450 K and resulted in good agreement with experiment. The effect of the vibrating framework on the diffusive process is discussed and a detailed analysis of the behavior of methane molecules in silicalite is reported
A comparative mlecular dynalics study of diffusion of n-decane and 3-methyl pentane in Y zeolite
No full text
A theoretical study of the solvent effect on dissociation reactions. The role of the first solvation shell
No full textWithin a model describing the solvent effect as mainly due to a restricted number of molecules simulating the first solvation shell, a theoretical study of dissociation reactions, performed by LCAO-MO-SCF approximation at CNDO/2 level, is presented. Several solutes in different solvents have been considered, and in particular the results of a study on the dissociation of CH 3F in H 2 are shown in detai
A theoretical investigation of the role of the solvent on the structure of the intermediates in solvolytic reactions. Part 4. Methanediazonium ion and methyl fluoride in hydrofluoric acid
No full textThe effect of a solvent other than water, . hydrofluoric acid, on the dissociation process of CHN and CHF was investigated by MO theory at the CNDO/2 level of approximation. As in water, CHN in HF dissociates without the formation of intermediates, while CHF forms stable ion pairs. The structure of dissolved ions and molecules is more affected by water than by HF, and water is more effective in promoting charge transfer and separation, in line with the physical properties of the solvents
Theoretical study of the solvation of nitrogen. Two different approaches
No full textAbstract
Two different approaches were used for a theoretical study of the solvation of N2, with HF, H2O, NH3, CH4 as solvents. In the first approach, the contour maps of orientationally optimized interaction energy between N2 and one solvent molecule were computed by fast semiempirical methods (Extended Hückel and CNDO/2) in order to find a reliable but not too expensive calculation method for solvation models. In the case of the N2-H2O system, an ab initio map was also evaluated for comparison. The second approach is based on the building up of clusters with one molecule of N2 surrounded by a number (2 to 8) of solvent molecules and finding the structure of such clusters by energy minimization. From the structures obtained it results that they are determined mainly by steric factors, so that clusters optimized by means of different methods are similar, despite the remarkable differences in the maps
Molecular dynamics study of the interlayer water in phyllosilicates
No full textA preliminary molecular dynamics study of the interlayer water in montmorillonite was performed by using a central force interaction model. The structural properties of the system, deduced from distribution functions, and the IR spectrum of water, calculated by Fourier transform of dipole moment autocorrelation function, are presented and compared with experimental dat
Molecular dynamics simulation of hydrate silicates. A test on natrolite
No full textA Molecular Dynamics (MD) study of natrolite, a fibrous Zeolite, was performed using an atom-atom interaction model suitable for all hydrate silicates. The structural properties of the system, deduced from distribution functions and the IR spectrum calculated by Fourier Transform of dipole moment autocorrelation function are presented and compared with experimental dat
- …
