Saturated aqueous NaCl solution and pure water in Na-montmorillonite clay at thermodynamic conditions of hydraulic fracturing: Thermodynamics, structure and diffusion from molecular simulations

Molecular Force Field Development for Aqueous Electrolytes: 2. Polarizable Models Incorporating Crystalline Chemical Potential and Their Accurate Simulations of Halite, Hydrohalite, Aqueous Solutions of NaCl, and Solubility

“…We implemented this approach with the target U cr equal to -780 and -786 kJ mol B = P (−e) − P (e) 6e (14) where P (±e) is the pressure of the expanded/compressed crystal and e = 0.01 was used.…”

A molecular simulation study into the stability of hydrated graphene nanochannels used in nanofluidics devices

“…For example, p hyd ( H ) is known to oscillate with respect to H with a periodicity approximately equal to the molecular diameter of the fluid, reflecting the geometric commensurability of integer fluid layers with H . 36,64,66…”

Engineered Barrier System Research Activities at LBNL (FY2020 Progress Report)

“…Classical molecular simulations serve as powerful tools to investigate the structure and energetics of equilibrium hydration states and the microstructures arising from phase coexistence of MMT. Several atomistic models have simulated the diffusion (Holmboe and Bourg, 2013), kinetics (Tournassat et al, 2016) and free energies of cation exchange (Rotenberg 2009;Teppen 2006;Lammers et al, 2017), and swelling thermodynamics (Hsiao and Hedström, 2017;Svoboda et al, 2018;Whitley and Smith, 2004) in various clay minerals. However, a quantitative evaluation of phase coexistence through the explicit modeling of mixed phases is missing in literature.…”

“…The calculation of free energy difference between stable hydrates yields the swelling free energy at a given solution composition. Significant focus has been dedicated to the estimation of swelling free energies using molecular modeling (Whitley & Smith, 2004;Smith et al, 2006, Honorio et al, 2017Svoboda et al, 2018;Underwood & Bourg, 2020). These studies have calculated the swelling free energy for trans-vacant MMT, which has a centrosymmetric molecular structure.…”

“…This discrepancy might have been an artifact of the selected force-field potential model; however, there is plenty of evidence in literature for NaMMT commonly occurring in the 2W state. Svoboda et al (2018) computed the PMF profiles for NaMMT suspended in pure water and 2.8 M salt solution, and concluded that the 3W state has the lowest free energy in pure water, whereas a lower hydration state (2W) was favored in the salt solution. X-ray diffraction (XRD) studies (Cases et al, 1992;Morodome and Kawamura, 2009) showed that the 3W hydrate occurs in significant proportions only at relative humidity (RH) of 0.93 or above.…”