Exploring liquid–liquid transitions in ZnSe at extreme conditions
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2017-12-01 |
| Journal | Acta Crystallographica Section A Foundations and Advances |
| Authors | S. Pascarelli, Can Yildirim, Jean‐Yves Raty, I. Kantor, R. Torchio |
| Institutions | European Science Foundation, Commissariat à l’Énergie Atomique et aux Énergies Alternatives |
Abstract
Section titled “Abstract”Here, we report on the fingerprints of 4-fold to 6-fold transition in liquid ZnSe at extreme pressure and temperature conditions up to 42 GPa and more than 3000 K using X-ray absorption spectroscopy (XAS) combined with laser-heated diamond anvil cell techniques and complementary ab initio molecular dynamics simulations.Among pressure induced structural modifications, liquid-liquid’ (L-L’) transitions have attracted much interest both experimentally and theoretically due to their peculiarity.Unlike most L-L’ transitions that only show slight modifications of the bond distances between atoms (i.e., P, Na, supercooled Si) [1, 2, 3], strong L-L’ transitions have been theoretically predicted for a few II-VI semiconductor compounds such as ZnSe, CdSe and CdTe, given the following two conditions are satisfied: Firstly, the melting of the sp3 bonded phase (4-fold coordination) at ambient pressure results in a liquid structure that remains approximately 4-fold coordinated; and secondly, the presence of a semiconductor to metal phase transition under pressure [4, 5, 6, 7].Our results show that solid and liquid ZnSe undergoes a series of structural modifications at various P, T values that satisfy the conditions above.The red shift in Zn K edge energy observed at around 7 GPa upon increasing temperature suggests a metallization event before melting to a possible 6-fold coordinated liquid structure.These findings are supported by our simulation results showing a pronounced difference in the first diffraction peak of the calculated structure factor at high pressures indicating a 4-fold to 6-fold coordination change in liquid ZnSe.Our results may provide additional insight for such transitions that may be observed for similar tetrahedrally coordinated II-VI systems.