© 2017 by the authors. We assess the feasibility of efficiently calculating accurate thermodynamic properties of (SiO 2 ) n ˙(H 2 O) m nanoclusters, using classical interatomic forcefields (FFs). Specifically, we use a recently parameterized FF for hydroxylated bulk silica systems (FFSiOH) to calculate zero-point energies and thermal contributions to vibrational internal energy and entropy, in order to estimate the free energy correction to the internal electronic energy of these nanoclusters. The performance of FFSiOH is then benchmarked against the results of corresponding calculations using density functional theory (DFT) calculations employing the B3LYP functional. Results are reported first for a set of (SiO 2 ) n ˙(H 2 O) m clusters with n = 4, 8 and 16, each possessing three different degrees of hydroxylation (R = m/n): 0.0, 0.25 and 0.5. Secondly, we consider five distinct hydroxylated nanocluster isomers with the same (SiO 2 )16˙(H 2 O)4 composition. Finally, the free energies for the progressive hydroxylation of three nanoclusters with R = 0-0.5 are also calculated. Our results demonstrate that, in all cases, the use of FFSiOH can provide estimates of thermodynamic properties with an accuracy close to that of DFT calculations, and at a fraction of the computational cost.
Macià Escatllar, A., Ugliengo, P., & Bromley, S. (2017). Computing Free Energies of Hydroxylated Silica Nanoclusters: Forcefield versus Density Functional Calculations. Inorganics, 5(3), 41. https://doi.org/10.3390/inorganics5030041