簇模型CaO(001)面上吸附汞与氯化汞的密度泛函理论研究

采用电荷自洽方法，以嵌入原子簇Ca9O9为模型，采用量子化学的密度泛函理论，对汞与氧化汞气体分子在CaO(001)面上的吸附进行了研究。计算表明，汞垂直底物表面吸附，只能与氧原子配位，吸附能为19．649kJ／mol，吸附高度为3．168A，属于较弱的物理吸附。氯化汞分别进行了垂直与平行底物两种构型计算，吸附能分别为23．699kJ／mol，87．829kJ／mol，吸附高度分别为3．289A，2．973A，说明氯化汞平行底物吸附为稳定构型，属于化学吸附。通过与相关的煤燃烧实验进行比较，结果比较吻合，表明量子化学的理论计算是筛选汞等痕量元素有效吸附剂及反应机理研究的一种有效方法。

A DENSITY FUNCTIONAL THEORY STUDY OF THE ADSORPTION OF HG AND HgCl2 ON A CaO(001) SURFACE

The adsorption of mercury and mercury chloride on a CaO(001)surface were investigated by the density functional theory(DFT) by using Ca9O9 cluster embedded in an electrostatic field represented by 178 point charges at the crystal CaO lattice positions. For the mercury molecular axis normal to the surface, the mercury can only coordinate to the O2- anion and has a very weak binding energy of 19.649kJ/mol. When the mercury chloride molecular axis is vertical to the surface, the Cl atom coordinate to the Ca2+ cation and has binding energy of 23.699 kJ/mol. When the mercury chloride molecular axis is parallel to the surface, the Hg atom coordinate to the O2- anion and has binding energy of 87.829 kJ/mol, which means that the parallel geometry is more stable than the vertical geometry. The present calculations show that CaO injection could substantially reducing gaseous mercury chloride, but have no apparent effect on the mercury, which is compatible with the available experimental results. The research method will provide the valuable information for the optimizing and selecting sorbent of the trace element in flue gas.