Solvation Structure and Dynamics of cis- and trans-1,2 Dichloroethene Isomers in Supercritical Carbon Dioxide. A Molecular Dynamics Simulation Study.

Abstract

Molecular dynamics simulation techniques have been employed to investigate the solvation structure and dynamics in dilute mixtures of cis- and trans-1,2-dichloroethene in supercritical carbon dioxide. The calculations were performed for state points along a near-critical isotherm (1.02 T(c)) over a wide range of densities, using new developed optimized potential models for both isomers. The similarities and differences in the solvation structures around each isomer have been presented and discussed. The local density augmentation and enhancement factors of CO(2) around the isomers have been found significantly larger than the corresponding values for pure supercritical CO(2). The dynamic local density reorganization has been investigated and related to previously proposed relaxation mechanisms. The density dependence of the calculated self-diffusion coefficients has revealed the existence of a plateau in the region of 0.7-1.1 ρ(c), where the local density augmentation exhibits the maximum value. The reorientational dynamics of the C═C bond vector have been also studied, exhibiting significant differences between the two isomers in the case of the second-order Legendre time correlation functions.

The molecular clusters in a supercritical fluid–solid system should be considered as a phase—thermodynamic principle and evidence

“…The general trend is that the degree of clustering is larger near the critical region of the SC solvents, and is smaller under the conditions far from the critical region, which is consistent with the conclusion obtained from extensive study in the literature. [17][18][19][20][21][22] It can be known by comparing the calculated phase equilibrium data (Fig. 2-5, Fig.…”

“…[14][15][16] The most interesting aspects of SCFs are that their density and the related properties are very sensitive to temperature and pressure and there exists density inhomogeneity in their critical region. [17][18][19][20][21][22] In a supercritical (SC) solution, the densities of the SC solvent and cosolvent (if exists) around the solute can be much larger than that of the bulk, especially in the critical region of the SC solvent, which is often called as clustering. [17][18][19][20][21][22] The existence of molecular clusters in SC solutions have been confirmed by various techniques, such as UV-Vis spectroscopy, [23][24][25][26][27] fluorescence, [28][29][30] small-angle X-ray scattering, [31][32][33] neutron diffraction technique, 34 electron paramagnetic resonance spectroscopy, 35 Monte Carlo [36][37][38][39] and molecular dynamics simulations, 11,40 and integral equation theory.…”

Modeling Solvation in Supercritical CO2

“…[71] As equential molecular dynamics (MD) andq uantum mechanics approach was used by Millot et al to compute the UV/Vis spectrum of organic dyes, [72] and more recently Born-Oppenheimer MD simulations were performed by Canuto's group to study the electronic spectrum of para-nitroaniline. [73,74] The organization of the solvent around the solute and its influence on the solution structural and dynamic properties were investigated by means of MD for small solutes, [75][76][77][78][79][80][81][82][83][84] polymers [85,86] and proteins, [87] and passivated gold nanoparticles. [88] Some work based on Car-Parrinello MD was also performed.…”

Transferable Potentials for Chloroethenes: Insights into Nonideal Solution Behavior of Environmental Contaminants

“…10 As such, there are no force field developed specifically for chloroethenes, but some studies 15,16 have used optimized potential for liquid simulations (OPLS) 17 -type force field for chloroalkenes. Dellis et al 18 examined the accuracy of OPLS force field for cis and trans -1,2-dichloroethene compounds. The computed thermophysical properties differ significantly from the experimental data.…”

“…This force field underestimates the saturated liquid density by 1.3–1.6% for cis isomer and 2.3–2.7% for the trans isomer. 18 This led authors to develop a new force field by refining the parameters against the available experimental data to investigate the solvation structure and dynamics of both the isomers in supercritical carbon dioxide. Luo and Farrell 19 used universal force field 20,21 for TCE and PCE to study how pH of the solution affects adsorption of these compounds on iron surfaces.…”