H原子在W低指数面上的吸附位和吸附态

Adsorption Sites and States for H Atom on W Low-index Surfaces

应用原子和表面簇合物相互作用的5参数Morse势及由5参数Morse势组装推广的LEPS方法对H-W低指数表面吸附体系进行了研究,并获得了全部临界点特性.计算结果表明,低覆盖度下,H原子优先吸附在W(100)面的内层吸附位二层桥位B',获得156meV的垂直振动频率,随着覆盖度的增加,H原子稳定吸附在表层的五重洞位(二层顶位)、桥位及顶位.内层吸附位的优先吸附,对与其邻近的表面吸附位的临界点性质有一定影响.在W(110)面上只存在三重洞位的稳定吸附态,垂直振动频率为151meV.在W(111)面上存在三种稳定吸附态,子表面吸附位H1,桥位B'和顶位T,分别获得104,200,259meV的垂直振动频率.在低覆盖度下,H原子优先吸附在子表面吸附位H1.

The adsorption of H atom on W low index surfaces was investigated with the 5-parameter Morse potential （5-MP） and the extended LEPS （constructed by 5-MP）. All critical characteristics of this system were obtained. The calculated results show that H atom preoccupies the twofold bridge site of the subsurface on the intact W（100） surface at low coverage, and obtains the perpendicular vibration frequency of 156 meV. The H-atom adsorption on bridge site, top site and fivefold hollow site （the top site on the second W layer） were observed at high coverage. The preoccupancy of the subsurface adsorption site affects the critical characteristics of the adsorption sites adjacent to the subsurface adsorption site. On （110） surface H atom occupies the three-fold hollow site and produces the vibration frequency of 151 meV. On （111） surface there exist three stable adsorption states, the subsurface adsorption site HI, the bridge sites and top sites, with the eigenvibration of 104, 200 and 259 meV, respectively. H atom preoccupies the H1 site at low coverage.