Extension of the [(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CH</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>N<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>]</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="italic">MX</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>family: Phase transitions and lattice parameters of sixteen [(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CH</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><i>Z</i><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>]</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="italic">MX</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>(<i>Z</i>=P,As,Sb;<i>M</i>=Co,Cu,Zn;<i>X</i>=Cl,Br,I) compounds
作者:Mark R. Pressprich、Marcus R. Bond、Roger D. Willett
DOI:10.1103/physrevb.43.13549
日期:——
Solid-solid phase-transition temperatures, entropies of transition, and room-temperature lattice parameters of sixteen [(CH3)4Z]2MX4 (Z = P,As,Sb; M = Co,Cu,Zn; X = Cl,Br,I) compounds are reported. [(CH3)4P]2CoBr4, [(CH3)4P]2CoI4, [(CH3)4P]2ZnBr4, [(CH3)4P]2ZnI4, [(CH3)4As]2CuBr4, [(CH3)4As]2CoI4, and [(CH3)4As]2ZnI4 have beta-K2SO4-type structures, analogous to known [(CH3)4N]2MX4 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 X2 and Z2 of Pmcn. Previously reported [(CH3)4Z]2MX4 (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 [(CH3)4P]2CoCl4, [(CH3)4P]2ZnCl4, [(CH3)4As]2CuCl4, [(CH3)4Sb]2CoCl4, [(CH3)4Sb]2CuCl4, [(CH3)4Sb]2ZnCl4 and [(CH3)4Sb]2CoBr4, [(CH3)4Sb]2CuBr4, [(CH3)4Sb]2ZnBr4, which have larger ratios of cation to anion radii, are grouped into a separate [(CH3)4As]2CoCl4 structure type, which is characterized by an apparent association with a cubic unit cell having almost-equal-to 12.7 angstrom axes.