TY - JOUR
T1 - Potential ultrahigh pressure polymorphs of AB X3 -type compounds
AU - Umemoto, Koichiro
AU - Wentzcovitch, Renata M
PY - 2006
Y1 - 2006
N2 - We have identified by first-principles computations two dynamically stable structures that are candidate ultrahigh pressure polymorphs of AB X3 -type compounds. To our knowledge, they have not been experimentally observed yet. They are produced by metastable pressure-induced transformations in Cmcm NaMg F3, a postperovskite phase. The first transition to a Pmcn structure is related to a soft phonon mode in postperovskite. The second one is a regular enthalpically driven transition from Pmcn to a P 63/mmc structure. In NaMg F3 these phases are metastable with respect to the dissociation into CsCl-type NaF and cotunnite-type Mg F2. However, other AB X3 -type compounds may favor these phases over the dissociation products. Even in NaMg F3, the Pmcn phase might be observed at low temperatures.
AB - We have identified by first-principles computations two dynamically stable structures that are candidate ultrahigh pressure polymorphs of AB X3 -type compounds. To our knowledge, they have not been experimentally observed yet. They are produced by metastable pressure-induced transformations in Cmcm NaMg F3, a postperovskite phase. The first transition to a Pmcn structure is related to a soft phonon mode in postperovskite. The second one is a regular enthalpically driven transition from Pmcn to a P 63/mmc structure. In NaMg F3 these phases are metastable with respect to the dissociation into CsCl-type NaF and cotunnite-type Mg F2. However, other AB X3 -type compounds may favor these phases over the dissociation products. Even in NaMg F3, the Pmcn phase might be observed at low temperatures.
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U2 - 10.1103/PhysRevB.74.224105
DO - 10.1103/PhysRevB.74.224105
M3 - Article
AN - SCOPUS:33845435519
SN - 1098-0121
VL - 74
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 22
M1 - 224105
ER -