Abstract
Single-crystal X-ray diffraction experiments show that the Be atoms in CeBe13 form a Be12 icosahedra, which is a very unusual structural feature due, in part, to the remarkably low valence electron count of Be. Magnetization studies show that CeBe13 displays intermediate valence behavior, in which valence fluctuations between the Ce 4f0 and 4f1 states give rise to enhanced electronic specific heat and magnetic susceptibility. Calculations using ab initio theory were used to determine the electronic structure and bonding and to give insight into the relationship between the crystal structure, the bonding, and the intermediate valence behavior of CeBe13. The hybridization between the localized f electrons and the conduction electrons is responsible for the large values of the electronic specific heat coefficient (gamma approximately 100 mJ/mol K2) and magnetic susceptibility (chi approximately 1 x 10-3 emu/mol), which is in marked contrast to those of ordinary metals that have gamma approximately 1 mJ/mol K2 and chi approximately 1 x 10-5 emu/mol values. The magnetic susceptibility, chi = M/H versus T, of a single crystal of CeBe13 exhibits a broad maximum at Tmax approximately 130 K and is typical of intermediate valence systems with an unusually large energy scale (Kondo), TK approximately 500 K.
Highlights
The single-crystal X-ray structure, magnetic susceptibility, and ab initio calculations are reported for this unprecedented Be geometry
Single crystals of CeBe13 were prepared by placing Ce, Be, and Al in the atomic ratio of 1:14:32 into an outgassed BeO crucible and by heating the mixture to 1200 °C under flowing helium
Excess Al was dissolved in NaOH solution, revealing CeBe13 single crystals with natural [100] faces
Summary
The single-crystal X-ray structure, magnetic susceptibility, and ab initio calculations are reported for this unprecedented Be geometry. The electronic structure and bonding in CeBe13 was studied via Gaussian 98 using ab initio-restricted Hartree-Fock single-point calculations. The 13 and 14au MOs have 18-30% f orbital Ce character (Figure 3).
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