Physics – Condensed Matter – Materials Science
Scientific paper
2011-04-27
Phys. Rev. B, vol. 84, 054509, 2011
Physics
Condensed Matter
Materials Science
10 pages, 7 figures
Scientific paper
10.1103/PhysRevB.84.054509
In a joint experimental and theoretical study, we investigate the isostructural collapse from the ambient pressure tetragonal phase to a collapsed tetragonal phase for non-superconducting metallic SrFe2As2 and SrFe_1.8Ru_0.2As_2. The crystallographic details have been studied using X-ray powder diffraction up to 20 GPa pressure in a diamond anvil cell. The structural phase transition occurs at 10 GPa and 9 GPa for SrFe2As2 and SrFe_1.8Ru_0.2As_2, respectively. The changes in the unit cell dimensions are highly anisotropic with a continuous decrease of the c lattice parameter with pressure, while the a-axis length increases until the transition to a collapsed tetragonal phase and then continues to decrease. Across the phase transition, we observe a volume reduction of 5% and 4% for SrFe2As2 and SrFe_1.8Ru_0.2As_2, respectively. We are able to discern that Ru substitution on the Fe-site acts like `chemical pressure' to the system. Density-functional theory-based calculations of the electronic structure and electron localizability indicator are consistent with the experimental observations. Detailed analysis of the electronic structure in k-space and real space reveals As 4pz interlayer bond formation as the driving force of the c/a collapse with a change in the As-As bond length of about 0.35ang.
Geibel Christoph
Grin Yuri
Hanfland Michael
Kasinathan Deepa
Koepernik Klaus
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