1,721,094 research outputs found
A new formulation of the PCM solvation method: PCM-QINTn RID E-4986-2010
No full textA new formulation of the PCM electrostatic solution problem is proposed. Through a new derivation of the PCM-CLSn expression we propose an interpolation formula that improved the convergence: PCM-QINTn. All the available formulations are applied to the evaluation of the electrostatic component of the free energy of solvation for some molecular systems. In addition, PCM-QINT derivatives of G(el) with respect to atomic coordinates are evaluated. The computational costs are compared with those of PCM-direct formulation
DefPol: a new procedure to build molecular surfaces and its use in continuum solvation methods
No full textAb initio study of the S(N)2 reaction CH3Cl+Cl-->Cl-+CH3Cl in supercritical water with the polarizable continuum model RID E-4986-2010
No full textWe present some calculations for an S(N)2 reaction in ambient and supercritical water performed with a continuum method for solvation, the polarizable continuum model (PCM). PCM allows us to perform quantum mechanical (QM) ab initio calculations at almost all the levels of the QM theory and allows us to treat solvent-separated solutes on the same footing as a tight reacting system. Both features are here exploited. The results indicate that the standard PCM version is able to reproduce computer simulation results at a good level of accuracy, with the exception of a specific range of P-T values of supercritical water characterized by a large isothermal compressibility. For calculations in this P-T range we present a PCM formulation giving results in good agreement with results from simulations
Reply to the comment on ?Computational studies on organic reactivity in ionic liquids? by C. Chiappe and C. S. Pomelli, Phys. Chem. Chem. Phys., 2013, 15, 412
No full textDefPol: New procedure to build molecular surfaces and its use in continuum solvation methods RID E-4986-2010
No full textWe present a method to define van der Waals, solvent-accessible, and solvent-excluding molecular surfaces with their partition in nonoverlapping surface portions (tesserae). The procedure is more efficient than those available in the literature to describe solvent effects on molecular systems of large size, and it tan also be applied to solutes of small size without reducing the accuracy of the output and without increasing computational times. All the tesserae are expressed in terms of spherical triangles, having all the characterizing elements (vertices, centers, etc.) analytically defined. The method was tested by comparing the results for the surface area and the solvation free energy (decomposed in electrostatic, dispersion, and steric contributions) obtained using the GEPOL procedure within the framework of the polarizable continuum model solvation method. These comparisons regard 87 molecules at the molecular mechanics level and 28 molecules at the ab initio Hartree-Fock level: the results art? quite satisfactory. (C) 1998 John Wiley & Sons, Inc
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