The structural properties of LaRu2P2 under external pressure have been studied up to 14 GPa, employing high-energy x-ray diffraction in a diamond-anvil pressure cell. At ambient conditions, LaRu2P2 (I4/mmm) has a tetragonal structure with a bulk modulus of B=105(2) GPa and exhibits superconductivity at Tc=4.1 K. With the application of pressure, LaRu2P2 undergoes a phase transition to a collapsed tetragonal (cT) state with a bulk modulus of B=175(5) GPa. At the transition, the c-lattice parameter exhibits a sharp decrease with a concurrent increase of the a-lattice parameter. The cT phase transition in LaRu2P2 is consistent with a second order transition, and was found to be temperature dependent, increasing from P=3.9(3) GPa at 160 K to P=4.6(3) GPa at 300 K. In total, our data are consistent with the cT transition being near, but slightly above 2 GPa at 5 K. Finally, we compare the effect of physical and chemical pressure in the RRu2P2 (R = Y, La-Er, Yb) isostructural series of compounds and find them to be analogous.
@article{arxiv.1706.04123,
title = {Collapsed Tetragonal Phase Transition in LaRu$_2$P$_2$},
author = {Gil Drachuck and Aashish Sapkota and Wageesha Jayasekara and Karunakar Kothapalli and Sergey L. Bud'ko and Alan I. Goldman and Andreas Kreyssig and Paul C. Canfield},
journal= {arXiv preprint arXiv:1706.04123},
year = {2017}
}