Theoretical study of the scheelite-to-fergusonite phase transition in YLiF4 under pressure

Recent experimental works on high-pressure X-ray diffraction have shown that YLiF4 undergoes a reversible phase transition around 10 GPa from the ambient pressure scheelite-type to a fergusonite-type structure. Different theoretical works have proposed either the M-fergusonite or M′-fergusonite as this second stable structure. Also, small changes in photoluminescence and Raman signals have been observed around 6 GPa, and have not been completely explained yet. In this work we present a first-principles Density Functional Theory structural study of YLiF4. We found that the anomalies at 6 GPa can be related to the structural changes observed in a scheelite to M′-fergusonite transition. We also have studied briefly different possibilities for an experimentally observed but not completly characterised third stable structure above 17 GPa.