I. I. Sheikhet

Theoretical investigation of changes in the thermodynamic properties of water in the region near an electrode upon the discharge of an hydroxonium ion

A method for investigating solutions in the region near an electrode has been developed in the framework of the Monte Carlo method. The energies of the reorganization of water upon the transfer of an electron to a hydroxonium ion from the unpolarized surface of an absolutely solid charged electrode in the range of surface charge densities from +0.056 to −0.640 C/m2 and upon the reverse process have been calculated. The hydration energies of an H3O+ cation and an H3O− radical in the region near an electrode have been calculated. The effective interactions of an ion and a nonpolar molecule with an electrode in a solution have been analyzed.

Calculation of the properties of liquid chloroform by the Monte Carlo method

A version of the Monte Carlo method for the study of the properties of pure liquids and solutions that was previously developed by Levchuk et al. was modified for the case of liquid chloroform. A single-center potential of the interaction of chloroform molecules was plotted by using trial Monte Carlo calculations. The potential makes it possible to calculate satisfactorily the energy and structural characteristics of chloroform.

Numerical methods in solution theory

Basic methods are considered for computer solution simulation: Monte Carlo, molecular dynamics, and optimization. Particular attention is given to methodological problems in realizing these schemes: the results are dependent on the equilibrium-part length, on the boundary models, and on the choice of interaction potentials. Examples are given of the methods used in chemical applications.

A theoretical method of researching ion-molecule reactions in solution

A method has been devised for researching the mechanisms of ion-molecule reactions in aqueous solutions, which involves deriving an approximate reaction path by means of a model Hamiltonian, in which the medium is described by a set of point Langevin dipoles. At the stationary points on the PES derived in that way, the solvation may be simulated by means of a more accurate scheme for the medium, namely by direct optimization of the potential energy for the solvate shell. The method has been tested on the reaction CO2+OH−⇄HCO3−. The model Hamiltonian has been constructed by MINDO/3. Good agreement with experiment is obtained.

Effects of boundary conditions on structure and energy calculations for aqueous methane solutions

The Monte Carlo method has been used with an NVT ensemble to calculate the structural and energy characteristics for an infinitely dilute aqueous methane solution. New boundary conditions have been used: the basic spherical cell is surrounded by a boundary layer of solvent molecules, whose positions are fixed in the calculation. The hydration energy is found as -7.63 +/- 8.40 kJ/mole, which agrees with the measured value of -10.9 kJ/mole better than do all other analogous Monte Carlo calculations. Results different from those published previously have also been obtained for the solution structure.

Structure of methylformamide and its enolic form in aqueous solutions

The electronic and structural characteristics of methylformamide and its enolic form were calculated by the MINDO/3 method with due regard to the effects of the solvent in the model of point charges. The coordinates of the point charges were determined both from calculation of the water cluster by the Monte Carlo method (112 water molecules) and from model theories about the structure of the intermolecular hydrogen bonds. An analysis is given of the dependence of the calculated characteristics on the structure of the solvated shell.