Abstract
Solid-solid phase-transition temperatures, entropies of transition, and room-temperature lattice parameters of sixteen [(Z (Z=P,As,Sb; M=Co,Cu,Zn; X=Cl,Br,I) compounds are reported. [(P, [(P, [(P, [(P, [(As, [(As, and [(As have β--type structures, analogous to known [(N compounds. Their room-temperature monoclinic space groups correspond to Landau-allowed continuous transitions from a suspected common high-temperature Pmcn phase. The associated distortion representations are compatible with and of Pmcn.
Previously reported [(Z (Z=N,P; M=Mn,Fe,Co,Ni,Cu,Zn; X=Cl,Br,I) compounds are also shown to have this compatibility feature for their sub-Pmcn phases. The set of compounds [(P, [(P, [(As, [(Sb, [(Sb, [(Sb and [(Sb, [(Sb, [(Sb, which have larger ratios of cation to anion radii, are grouped into a separate [(As structure type, which is characterized by an apparent association with a cubic unit cell having ≊12.7 Å axes.
- Received 12 July 1990
DOI:https://doi.org/10.1103/PhysRevB.43.13549
©1991 American Physical Society