石墨表面吸附钾系统电子性质的理论研究

基于集团模型电荷自洽的EHT(Extended Hückel Tneory)方法对K在石墨(0001)表面吸附态进行了优化计算.在3种不同的覆盖度(Θ)下,对k-石墨系统的电荷转移量△Q、吸附能△E、态密度PDOS和TDOS、Mulliken集居数和成键性质进行了比较.认同K/石墨吸附系统是石墨插层化合物(GIC)的雏型.并用LMTO方法对KC₈完成电子结构的第一性原理研究,得到与EHT完全一致的结果:K4s-Ca杂化态主要位于低能区域远离费米能级,构成反键轨道其电子转移到费米能级附近K3d-Cπ成键的杂化轨道上.空的3d轨道在目前EHT方法和LMTO方法计算中扮演了关键角色.这与其他文献K-4s态处在EF能级的结果不同,但与早期Fischer(1984),Johnson(1986)XPS,ARUPS的实验结果吻合.

Theoretical Study on Electronic Properties of Potassium Adsorption on Graphite Surface

Based on a cluster model the adsorption of K on the graphite(0001)sufface has been studied different coverages (Θ). The equilibrium adsorption heights obtained are in good agreement with experimental data and other theoretical values. The charge transfer △Q, adsorption energy △E, density of states(PDOS and TDOS), Mulliken population and the bonding nature of the K/graphite systems are presented. It is worth noting that the Linear Muffin-tin Orbital(LMTO) method with the local functional theory has attained quite reliable results that are in qualitative agreement with those of the EHT. The results also show strong sensitivity of the electronic structure on the very little change of K-graphite layer spacing. This implies that K-graphite system is not a stable"single-phase"system. It is found that the K-4s and carbon-δ hybrid states are mainly situated in the lowest energy range discussed, which is the reason why K-4s states cannot be found at the Fermi level for K-graphite systems in the X-ray photoelectron spectroscopy(XPS) and angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) measurements. The empty 3d-orbitals are believed to play a central role in present calculations with two different methods.