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Updated: Jun 3, 2026

Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 7, 2013
Formation of collapsed tetragonal phase in EuCo₂As₂ under high pressure
Matthew Bishop1, Walter Uhoya, Georgiy Tsoi
1Department of Physics, University of West Georgia, Carrollton, GA 30118, USA.
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.
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