Anisotropy in Stable Conformations of HydroxylateIons between the {001} and {110} Planes of TiO 2 RutileCrystals for Glycolate, Lactate, and 2‑Hydroxybutyrate IonsStudied by Metadynamics Method

Control over TiO2 rutile crystal growth and morphology using additives is essential for the development of functional materials. Computer simulation studies on the thermodynamically stable conformations of additives at the surfaces of rutile crystals contribute to understanding the mechanisms underlying this control. In this study, a metadynamics method was combined with molecular dynamics simulations to investigate the thermodynamically stable conformations of glycolate, lactate, and 2-hydroxybutyrate ions at the {001} and {110} planes of rutile crystals. Two simple atom–atom distances were selected as collective variables for the metadynamics method. At the {001} plane, a conformation in which the COO– group was oriented toward the surface was found to be the most stable for the lactate and 2-hydroxybutyrate ions, whereas a conformation in which the COO– group was oriented toward water was the most stable for the glycolate ion. At the {110} plane, a conformation in which the COO– group was oriented towa...