THE HIGH PRESSURE BEHAVIOR OF Mo2GaC AND Mo2Ga2C

Mark Nikolaevsky ¹ Roee Friedman ^2,3 Mishael Hornik ^2,4 Sankalp Kota ⁵ Joseph Halim ⁵ El'ad Nisan Caspi ¹ Michel Barsoum ⁵ Martin Dahlqvist ⁶ Johanna Rosen ⁶ Aviva Melchior ¹

¹Physics Department, Nuclear Research Center Negev, Beer-Sheva, Israel
²Physics Department, Israel Atomic Energy Commission, Tel Aviv, Israel
³School of Physics and Astronomy, Tel Aviv Univesity, Tel Aviv, Israel
⁴Physics Department, Ben-Gurion University of the Negev, Beer-Sheva, Israel
⁵Department of Physics, Drexel University, Philadelphia, Pennsylvania, USA
⁶Department of Physics, Chemistry and Biology, Linkoping University, Linkoping, Sweden

M_n+1AX_n (MAX) phases with n=1-3 are a class of hexagonal nanolaminated materials, where M is an early transition metal, A is a main group element, and X is C or N. They are characterized by slabs of carbide or nitride (M_n+1X_n) separated by monolayers of pure A element. Having this layered structure the MAX phases exhibit a combination of the properties of both ceramic and metallic compounds, making them attractive for many technological applications. Mo₂GaC and Mo₂Ga₂C are of great interest because of their structural similarity; Mo₂Ga₂C is also laminated, but it contains a Ga double-layer interleaving between the Mo₂C blocks, instead of a Ga monolayer in Mo2GaC.

The mechanical properties and structural evolution under pressure of both Mo₂GaC and Mo₂Ga₂C were calculated by first-principles [1, 2]. For both compounds a substantial difference in the compressibilities along the axes was found – the a axis is much softer than the c axis. For Mo₂GaC the compressibility anomaly of c is closely reflected by the internal coordinate shift of Mo atom that shows three different slopes within 0–15, 20–60, and 70–100 GPa, respectively [1]. For Mo₂Ga₂C, a phase transition is predicted at 48 GPa with an increase of c and a decrease in a [2].

The current work concentrates in experimental investigation of the high pressure behavior of Mo₂GaC and Mo₂Ga₂C. XRD measurements of samples loaded in diamond anvil cells were used to retrieve the structure of the compounds under pressure. The experimental results will be compared to the theoretical predictions.

1. Q.-H. Gao et. al., J. Appl. Phys. 119, 015901 (2016).

2. Z.-J. Yang et. al.,Mod. Phys. Lett. B30, 1650105 (2016).