Freezing point and solid-liquid interfacial free energy of Stockmayer dipolar fluids: A molecular dynamics simulation study

Abstract

Stockmayer fluids are a prototype model system for dipolar fluids. We have computed the freezing temperatures of Stockmayer fluids at zero pressure using three different molecular-dynamics simulation methods, namely, the superheating-undercooling method, the constant-pressure and constant-temperature two-phase coexistence method, and the constant-pressure and constant-enthalpy two-phase coexistence method. The best estimate of the freezing temperature (in reduced unit) for the Stockmayer (SM) fluid with the dimensionless dipole moment μ*=1, √2, √3 is 0.656 ± 0.001, 0.726 ± 0.002, and 0.835 ± 0.005, respectively. The freezing temperature increases with the dipolar strength. Moreover, for the first time, the solid-liquid interfacial free energies γ of the fcc (111), (110), and (100) interfaces are computed using two independent methods, namely, the cleaving-wall method and the interfacial fluctuation method. Both methods predict that the interfacial free energy increases with the dipole moment. Although the interfacial fluctuation method suggests a weaker interfacial anisotropy, particularly for strongly dipolar SM fluids, both methods predicted the same trend of interfacial anisotropy, i.e., γ100 > γ110 > γ111.

Stress testing the ELBA water model

“…In particular, decreasing the dipole magnitude should have the effect of decreasing the melting temperature, consistently with what has been reported for generic 'Lennard-Jones plus point dipole' models in reduced units. [68,69] However, changing the dipole will of course have repercussions not only on the melting point, but also on all other physical properties; a reparametrisation of the whole force field could therefore be needed, with no guarantee of eventually obtaining an overall better model. Finally, regarding the shear viscosity h, ELBA yielded a result only 7% larger than the experimental value; the corresponding accuracy is higher than that of the atomistic models (which have relative errors between 18% and 64%) as well as the other coarse-grained models BMW (relative error from 13% to 81%) and GROMOS (relative error of 316%).…”

A study of the ice–water interface using the TIP4P/2005 water model

“…In this paper we evaluate γ iw for the TIP4P/2005 model by means of the Capillary Fluctuation Method [13]. This method has been used, for instance, for the calculation of the interfacial free energy of hard spheres [14], the Lennard-Jones [15] and dipolar fluids [16]. Here we evaluate γ iw for the TIP4P/2005 model for the basal, prismatic I and prismatic II planes of ice.…”

Crystal-liquid interfacial free energy via thermodynamic integration

“…Subsequently, several authors have adopted the "cleaving walls" scheme to compute γ cl for various model systems [39][40][41]. The data reported by them were precise enough to resolve the anisotropy in γ cl .…”