Voloshina Elena, Paulus Beate
Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, 01187 Dresden, Germany.
J Comput Chem. 2008 Oct;29(13):2107-12. doi: 10.1002/jcc.20991.
The effect of electron-correlation on the ground-state properties of CeN and LaN is studied by ab initio quantum-chemical methods. The approach which is used combines two separate steps: (1) the ground-state Hartree-Fock calculations for the crystal; (2) application of the method of increments to the studied system, which allows an expansion of bulk properties using the information from quantum-chemical calculations performed for finite clusters. As can be expected, for CeN correlation plays a significant role: with Hartree-Fock method only 49% of the experimental cohesive energy has been recovered, whereas after correlation corrections (coupled-cluster approach) the ground-state properties were found to be in good agreement with the experimental data found in literature. Thus, we obtained about 90% of the expected cohesive energy; the computed lattice constants and bulk moduli also agree well with the experimental values. For comparison, the equivalent treatment has been performed for LaN, where no f orbital is occupied. There the HF contribution to the ground-state properties is larger and hence the correlation effects weaker.
采用从头算量子化学方法研究了电子关联对CeN和LaN基态性质的影响。所采用的方法包括两个独立的步骤：(1) 对晶体进行基态哈特里-福克计算；(2) 将增量法应用于所研究的体系，该方法允许利用对有限团簇进行量子化学计算得到的信息来扩展体相性质。正如所预期的那样，对于CeN，关联起着重要作用：仅用哈特里-福克方法只能得到49%的实验结合能，而经过关联校正（耦合簇方法）后，发现基态性质与文献中的实验数据吻合良好。因此，我们得到了约90%的预期结合能；计算得到的晶格常数和体模量也与实验值吻合得很好。作为对比，对没有f轨道占据的LaN进行了等效处理。在那里，哈特里-福克对基态性质的贡献更大，因此关联效应较弱。
