title: Formation of As-As Interlayer Bonding in the collapsed tetragonal phase of NaFe2As2 under pressure.
abstract: NaFe2As2 is investigated experimentally using powder x-ray diffraction and Raman spectroscopy at pressures up to 23 GPa at room temperature and using ab-initio calculations. The results reveal a pressure-induced structural modification at 4 GPa from the starting tetragonal to a collapsed tetragonal phase. We determined the changes in interatomic distances under pressure that allowed us to connect the structural changes and superconductivity. The transition is related to the formation of interlayer As-As bonds at the expense of weakening of Fe-As bonds in agreement with recent theoretical predictions.
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, U.S.A.
authors.forename: Elissaios
authors.initials: E
authors.lastname: Stavrou
authors.affiliation: 1] Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China [2] Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, U.S.A [3] Key Laboratory of Materials Physics, Institute of Solid State Physics, CAS, Hefei, 230031, China.
authors.forename: Xiao-Jia
authors.initials: XJ
authors.lastname: Chen
authors.affiliation: 1] Department of Geosciences, Center for Materials by Design, Institute for Advanced Computational Science, Stony Brook University, Stony Brook, NY 11794-2100, U.S.A [2] Moscow Institute of Physics and Technology, 9 Institutskiy lane, Dolgoprudny city, Moscow Region, 141700, Russian Federation [3] School of Materials Science, Northwestern Polytechnical University, Xi'an, 710072, China.
authors.forename: Artem R
authors.initials: AR
authors.lastname: Oganov
authors.affiliation: Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: A F
authors.initials: AF
authors.lastname: Wang
authors.affiliation: Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Yan
authors.affiliation: Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: X G
authors.initials: XG
authors.lastname: Luo
authors.affiliation: Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: X H
authors.initials: XH
authors.lastname: Chen
authors.affiliation: 1] Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, U.S.A [2] Key Laboratory of Materials Physics, Institute of Solid State Physics, CAS, Hefei, 230031, China [3] University of Science and Technology of China, Hefei, 230026, China.
authors.forename: Alexander F
authors.initials: AF
authors.lastname: Goncharov