(253ac) Desolvation Barriers in Ionic Crystal Growth

Mark N. Joswiak,^a Michael F. Doherty,^a Baron Peters^a,b

^a Department of Chemical Engineering, University of California-Santa Barbara

^b Department of Chemistry and Biochemistry, University of California-Santa Barbara

Crystal habits are dependent on characteristics of the solute, but the solvent can dramatically impact the morphology [1]. The role of the solvent is two-fold â?? altering surface energies and/or attachment barriers. While numerous studies have explored the â??solvent effectâ? in terms of surface energies [2], few studies have explored desolvation/attachment barriers [3-6], which have been implicated as the rate-limiting step for crystal growth. Understanding these kinetic barriers is critical for accurate models of crystal growth and dissolution. We use rare-event simulation techniques and mechanistic hypothesis testing [7] to investigate the role of water molecules on the detachment of ions from kink sites of a NaCl crystal. We are able to characterize the detachment/attachment process in terms of general, simple reaction coordinates involving 1 solute and 1 solvent collective variable. We discuss the similarities and differences between the two ions during the detachment process. From our computed detachment rates, we calculate the rate of NaCl dissolution and find excellent agreement with an independent study [8]. We discuss the applicability of our results to other important and interesting systems, such as calcium carbonate crystal growth.

References:

[1] P. Dandekar, Z.B. Kuvadia, M.F. Doherty, Annu. Rev. Mater. Res. 2013, 43, 359-386.

[2] S.H. Kim, P. Dandekar, M.A. Lovette, M.F. Doherty, Cryst. Growth Des. 2014, 14, 2460-2467.

[3] P.G. Vekilov, Cryst. Growth Des. 2007, 7, 2796-2810.

[4] A.G. Stack, P. Raiteri, J.D. Gale, J. Am. Chem. Soc. 2012, 134, 11-14.

[5] S. Piana, F. Jones, J.D. Gale, J. Am. Chem. Soc. 2006, 128, 13568-13574.

[6] L.M. Liu, A. Laio, A. Michaelides, Phys. Chem. Chem. Phys. 2011, 13, 13162-13166.

[7] B. Peters, Mol. Simulat. 2010, 36, 1265-1281.

[8] G. Lanaro, G.N. Patey, J. Phys. Chem. B 2015, 119, 4275-4283.