The crystal-fluid interfacial free energy and nucleation rate of NaCl from different simulation methods.

Abstract

In this work, we calculate the crystal-fluid interfacial free energy, γ(cf), for the Tosi-Fumi model of NaCl using three different simulation techniques: seeding, umbrella sampling, and mold integration. The three techniques give an orientationaly averaged γ(cf) of about 100 mJ/m(2). Moreover, we observe that the shape of crystalline clusters embedded in the supercooled fluid is spherical. Using the mold integration technique, we compute γ(cf) for four different crystal orientations. The obtained interfacial free energies range from 100 to 114 mJ/m(2), being (100) and (111) the crystal planes with the lowest and highest γ(cf), respectively. Within the accuracy of our calculations, the interfacial free energy either does not depend on temperature or changes very smoothly with it. Combining the seeding technique with classical nucleation theory, we also estimate nucleation free energy barriers and nucleation rates for a wide temperature range (800-1040 K). The obtained results compare quite well with brute force calculations and with previous results obtained with umbrella sampling [Valeriani et al., J. Chem. Phys, 122, 194501 (2005)].