title: Pressure-induced pseudoatom bonding collapse and isosymmetric phase transition in Zr2Cu: first-principles predictions.
abstract: The structural evolution of tetragonal Zr2Cu has been investigated under high pressures up to 70 GPa by means of density functional theory. Our calculations predict a pressure-induced isosymmetric transition where the tetragonal symmetry (I4/mmm) is retained during the entire compression as well as decompression process while its axial ratio (c/a) undergoes a transition from ~3.5 to ~4.2 at around 35 GPa with a hysteresis width of about 4 GPa accompanied by an obvious volume collapse of 1.8% and anomalous elastic properties such as weak mechanical stability, dramatically high elastic anisotropy, and low Young's modulus. Crystallographically, the tetragonal axial ratio shift renders this transition analogous to a simple bcc-to-fcc structural transition, which implies it might be densification-driven. Electronically, the ambient Zr2Cu is uncovered with an intriguing pseudo BaFe2As2-type structure, which upon the phase transition undergoes an electron density topological change and collapses to an atomic-sandwich-like structure. The pseudo BaFe2As2-type structure is demonstrated to be shaped by hybridized dxz + yz electronic states below Fermi level, while the high pressure straight Zr-Zr bonding is accommodated by electronic states near Fermi level with dx(2) - y(2) dominant features.
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Jinliang
authors.initials: J
authors.lastname: Ning
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Suhong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Na
authors.initials: N
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Limin
authors.initials: L
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Mingzhen
authors.initials: M
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, People's Republic of China.
authors.forename: Riping
authors.initials: R
authors.lastname: Liu