钾在石墨中的嵌入：van der Waals密度泛函研究
Potassium intercalation in graphite: A van der Waals density-functional study
摘要：
用第一性原理研究了钾在石墨中的嵌入过程。传统的半局域密度泛函理论（DFT）计算合理地解释了钾-石墨化合物中的键合。然而，要研究纯钾原子和石墨的插层形成能，需要使用石墨层间结合的描述，从而对非局部色散相互作用进行一致的描述。这是无缝地包括与普通DFT的范德华密度泛函（vdW-DF）的方法[物理评论快报。92，246401（2004）]。发现使用vdW-DF稳定石墨晶体，晶体参数与实验相当一致。对于石墨和钾插层石墨的结构参数，如结合分离，层结合能，形成能，和体积模量的报告。此外，吸附和亚表面钾吸收能量的报告。vdw-DF描述，与传统的半局部方法相比，被发现弱软化的弹性响应。
英文摘要：
Potassium intercalation in graphite is investigated by first-principles theory. The bonding in the potassium-graphite compound is reasonably well accounted for by traditional semilocal density functional theory (DFT) calculations. However, to investigate the intercalate formation energy from pure potassium atoms and graphite requires use of a description of the graphite interlayer binding and thus a consistent account of the nonlocal dispersive interactions. This is included seamlessly with ordinary DFT by a van der Waals density functional (vdW-DF) approach [Phys. Rev. Lett. 92, 246401 (2004)]. The use of the vdW-DF is found to stabilize the graphite crystal, with crystal parameters in fair agreement with experiments. For graphite and potassium-intercalated graphite structural parameters such as binding separation, layer binding energy, formation energy, and bulk modulus are reported. Also the adsorption and sub-surface potassium absorption energies are reported. The vdW-DF description, compared with the traditional semilocal approach, is found to weakly soften the elastic response.
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