Answers are grounded in this paper and cite their sources.
X‐ray diffraction patterns of calcium samples of different purities have shown that 99.9 + % Ca exists in only two allotropic forms: face‐centered cubic to 464°C and body‐centered cubic from 464°C to the melting point. These results for the high temperature allotrope differ from the widely accepted structure; handbooks and tables currently list the high temperature allotrope as hexagonal closest‐packed. It has been further shown that a previously reported intermediate allotrope of complex structure is due to contamination. The temperature dependence of the electrical resistivity of the 99.9 + % Ca was found to be linear for both the face‐centered cubic allotrope and for the body‐centered cubic allotrope. Calcium was observed to be self‐annealing at room temperature.
No takes yet. Share an insight, caveat, or question.
Smith et al. (1956) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: