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。极性表面可以通过用具有净电荷的平面终止离子固体来产生。当铁电化合物的表面不平行于体极化时，铁电化合物的表面也是极性的。在铁电化合物的情况下，气相极性表面对非化学计量的重构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电解质中的离子屏蔽表面电荷（双电层形成）来稳定。第二个目标是通过计算化学吸附能、表面酸性和电活性物质的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。这些（自由）能将与相同化合物的非极性表面的相应能量进行比较。使用的计算方法是基于密度泛函理论的分子动力学（DFTMD），扩展了最近开发的有限场技术，用于处理周期模型系统中的双电层（arXiv预印本arXiv：1609.07754（2016））。这项研究是极性表面在多相催化中的潜力的计算探索的第一步。模型系统，将被认为是主族氧化物，如Al 2 O 3，d 0过渡金属氧化物，如ZrO 2和铁电固体，如PbTiO 3中使用的非均相酸碱化学。

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.