A molecular dynamics study of sodium dodecyl sulfate‐methane system in water using the improved lennard jones formulation

Abstract

ABSTRACT:The behavior of the sodium dodecyl sulfate (SDS)-methane system in water has been investigated using molecular dynamics calculations performed on a local cluster as well as on the EGI-grid distributed platform. To this end, the model adapted molecular polarizability centers for force-fields has been adopted to provide in a reliable and suitable analytical form the various intermolecular potentials involved. Structural properties of the system have been then investigated by varying the number of water molecules solvating the SDS and the CH 4 molecules.

Ar Solvation Shells in K+–HFBz: From Cluster Rearrangement to Solvation Dynamics

“…All these effects, have been considered by us in the development of a semiempirical potential model, based on the decomposition of the nonelectrostatic component of the interaction energy in pair “effective” contributions between centers of two different partners. Our effort was focused on the choice of potential functions ,,,− defined by a limited number of parameters having a physical meaning, related to basic physical properties of the interacting partners. Most of the parameters so defined become transferable from simple to complex systems.…”

Carbon Dioxide Clathrate Hydrates: Selective Role of Intermolecular Interactions and Action of the SDS Catalyst

“…For the title system, the formation and stability of the host solvent cages around the guest gas molecule are governed by the host–guest (H 2 O–CO 2 ) and host–host (H 2 O–H 2 O) interactions (and to a minor extent by the guest–guest CO 2 –CO 2 ones) when no third species, as is, for instance, the SDS (tensioactive) additive considered in our case, is introduced. The procedure followed by us is already documented: ,− the H 2 O–CO 2 contribution was formulated without any partitioning of the H 2 O polarizability because of its small value (1.47 Å 3 ) when compared with that of CO 2 (2.65 Å 3 ). Accordingly, a single interaction center placed on O, having a polarizability value equal to that of the water molecule and labeled as OW, was used.…”

“…To the end of carrying out a detailed comparison with the results of our previous methane clathrate hydrate study, , we considered at first a system made of one CO 2 molecule surrounded by an ensemble of 256 water ones (weight fraction equal to 0.0095). The system was thermalized to reach a temperature of 200 K using a microcanonical ensemble of particles.…”

“…The system was thermalized to reach a temperature of 200 K using a microcanonical ensemble of particles. Then, isothermal–isobaric MD simulations were carried out at a pressure of 8 MPa in the 200–300 K temperature range. , Trajectories were run for 10 ns using a time step of 0.001 ps. The same calculations were later repeated using 5 and 50 molecules of CO 2 placed initially at the center of a box containing an ensemble of 256 surrounding H 2 O molecules (weight fractions of 0.048 and 0.48, respectively).…”

“…Accordingly, the intramolecular energy V intra determining the stability of the SDS conformation was evaluated from bond, angle (see ref ), and dihedral contributions with the interaction between groups separated by more than three bonds being calculated using the parameters of Table for V nelec and the charge distribution of refs and for V elec . For the SDS–H 2 O interaction component, we took the same as that of our previous methane hydrate investigation, , in which, at low temperature, the equilibrium geometry of the isolated SDS does not get modified by the presence of H 2 O. In particular, water interacts with the polar head of the SDS molecule without altering its geometry.…”