Abstract
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. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008