Computational Investigation of Polar Surface/Electrolyte Interfaces

固体的极性表面是具有净有效电荷密度的表面。极性表面可以通过一个带净电荷的平面终止离子固体而形成。当表面不平行于体极化时，铁电化合物的表面也是极性的。对于铁电化合物，气相极性表面对非化学计量重建或去极化是不稳定的。该项目的第一个目标是验证极性表面是否可以通过筛选表面电荷（双电层形成）的电解质中的离子来稳定。第二个目的是通过计算电活性物质的化学吸附能、表面酸度和氧化还原电位来研究这种极性表面-电解质界面的表面化学。将这些（自由）能与同一化合物的非极性表面的相应能进行比较。使用的计算方法是基于密度泛函理论的分子动力学（DFTMD），扩展了最近开发的用于处理周期模型系统中的双电层的有限场技术（arXiv预印本arXiv:1609.07754(2016)）。这项研究是在多相催化极性表面的潜力的计算探索的第一步。将考虑的模型系统主要是氧化物，如Al2O3，过渡金属氧化物，如ZrO2和铁电固体，如非均相酸碱化学中使用的PbTiO3。

Polar surfaces of solids are surfaces with a net effective charge density. Polar surfaces can be created by terminating an ionic solid by a plane with a net charge. Also surfaces of ferroelectric compounds are polar when the surface is not parallel to the bulk polarization. Gas phase polar surfaces are unstable against non-stoichiometric reconstruction or depolarization in case of ferroelectric compounds. A first objective of the project is to verify whether polar surfaces can be stabilized by ions in an electrolyte screening the surface charge (electric double layer formation). The second aim is to investigate the surface chemistry of such polar surface-electrolyte interfaces by computing chemisorption energies, surface acidities and redox potentials of electro-active species. These (free) energies will be compared to the corresponding energies of non-polar surfaces of the same compound.The computational method to be used is Density Functional Theory based Molecular Dynamics (DFTMD) extended with a recently developed finite field technique for the treatment of electric double layers in periodic model systems (arXiv preprint arXiv:1609.07754 (2016)). This study is a first step in a computational exploration of the potential of polar surfaces in heterogeneous catalysis. Model systems that will be considered are main group oxides, such as Al2O3, d0 transition metal oxides such as ZrO2 and ferroelectric solids such as PbTiO3 used in heterogeneous acid base chemistry.