第一性原理研究H_2O分子在CaCO_3(104)表面吸附

基于密度泛函理论的第一性原理方法模拟研究H_2O在CaCO_3(104)表面的吸附特征.首先,研究H_2O分子在CaCO_3(104)表面的顶位、桥位(短桥位、长桥位)和穴位上垂直和平行表面两种类型下的8种高对称吸附结构模型,结合吸附能和稳定吸附构象确定最优吸附位.而后,基于H_2O/CaCO_3(104)最优吸附结构模型,研究吸附前后H_2O和CaCO_3(104)表面的物理结构、电子结构(Mulliken电荷布居数、态密度、电子局域函数)的特征,分析H_2O/CaCO_3(104)表面之间的相互作用以及成键机理.研究结果:吸附能和体系稳定构象显示H_2O分子/CaCO_3(104)表面的最稳定吸附结构为穴位-平行.在穴位-平行位吸附后,H_2O分子的O-H键长和H-O-H键角均发生改变; CaCO_3晶体平行和垂直(104)表面方向上原子位置均发生改变,表面层变化最大;即吸附作用对H_2O分子和CaCO_3晶体的物理结构均产生较大影响; H_2O/CaCO3(104)最优吸附体系的Mulliken电荷布居数、电子态密度、电子局域函数的研究均说明H_2O分子与CaCO3(104)之间存在电子的转移形成化学键.其中,Ca-O(H_2O)形成离子键,H(H_2O)-O(CaCO_3)之间存在氢键作用.本文研究揭示了方解石表面水湿性的原因,同时为方解石润湿性的深入研究奠定基础.

First Principles Study on the Adsorption of H2O Molecule on CaCO3(104) Surface

The adsorption characteristics of H2O on CaCO3 (104) surface were studied by the first principle. First, we study 8 high symmetry adsorption structural models of H2O molecules on the top position, bridge position (short bridge position, long bridge position) and hollow position on the CaCO3 (104)surface, respectively, with vertical and parallel surfaces. Combined with adsorption energy and stable adsorption conformation, the optimal adsorption site was determined. Then, based on the H2O / CaCO3 (104) optimal adsorption structure model, we study the variation of the physical structure and the electronic structure (Mulliken population analysis, the density of state, electron localization function) of the H2O / CaCO3 (104) system. Based on that we analyzed the interaction between H2O / CaCO3 (104) surface. Results showed that the most stable adsorption structure is hollow-parallel, based on the stable conformation and the adsorption energy of H2O / CaCO3 (104) system. After the adsorption of H2O on the CaCO3 (104)surface, the O-H bond length and the H-O-H bond angle of H2O molecules are all changed, and the atomic positions of CaCO3 (104) crystals in the direction of parallel and vertical to (104) surface are also changed, in which atoms of the surface layer changes most. That is, the adsorption has great influence on the physical structure of H2O and CaCO3 crystals. Study on the Mulliken population analysis, the density of state and the electron localization function of the H2O / CaCO3 (104) showed that there exist electron transfer between H2O molecule and CaCO3 (104) and bond is formed. Ca-O (H2O) is an ionic bond and H (H2O) -O (CaCO3 ) is hydrogen bonds.