Anomalous elastic properties across the γ to α volume collapse in cerium.
Nat Commun
; 8(1): 1198, 2017 10 31.
Article
in En
| MEDLINE
| ID: mdl-29084963
ABSTRACT
The behavior of the f-electrons in the lanthanides and actinides governs important macroscopic properties but their pressure and temperature dependence is not fully explored. Cerium with nominally just one 4f electron offers a case study with its iso-structural volume collapse from the γ-phase to the α-phase ending in a critical point (p C, V C, T C), unique among the elements, whose mechanism remains controversial. Here, we present longitudinal (c L) and transverse sound speeds (c T) versus pressure from higher than room temperature to T C for the first time. While c L experiences a non-linear dip at the volume collapse, c T shows a step-like change. This produces very peculiar macroscopic properties the minimum in the bulk modulus becomes more pronounced, the step-like increase of the shear modulus diminishes and the Poisson's ratio becomes negative-meaning that cerium becomes auxetic. At the critical point itself cerium lacks any compressive strength but offers resistance to shear.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Language:
En
Journal:
Nat Commun
Year:
2017
Document type:
Article