title: Formation of collapsed tetragonal phase in EuCo₂As₂ under high pressure.
abstract: The structural properties of EuCo₂As₂ have been studied up to 35 GPa, through the use of x-ray diffraction in a diamond anvil cell at a synchrotron source. At ambient conditions, EuCo₂As₂ ) (I4/mmm) has a tetragonal lattice structure with a bulk modulus of 48 ± 4 GPa. With the application of pressure, the a axis exhibits negative compressibility with a concurrent sharp decrease in c-axis length. The anomalous compressibility of the a axis continues until 4.7 GPa, at which point the structure undergoes a second-order phase transition to a collapsed tetragonal (CT) state with a bulk modulus of 111 ± 2 GPa. We found a strong correlation between the ambient pressure volume of 122 parents of superconductors and the corresponding tetragonal to collapsed tetragonal phase transition pressures.
authors.affiliation: Department of Physics, University of West Georgia, Carrollton, GA 30118, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Bishop
authors.forename: Walter
authors.initials: W
authors.lastname: Uhoya
authors.forename: Georgiy
authors.initials: G
authors.lastname: Tsoi
authors.forename: Yogesh K
authors.initials: YK
authors.lastname: Vohra
authors.forename: Athena S
authors.initials: AS
authors.lastname: Sefat
authors.forename: Brian C
authors.initials: BC
authors.lastname: Sales