Boron arsenate and its pressure-dependent auxetic properties

The mechanical properties of single crystals boron arsenate, BAsO4, are simulated through density functional theory simulations over a wide range of pressures from -10 to +90 GPa. It was shown that the elastic constants, as well as the extent of auxeticity, are highly pressure dependent. In particular, the Poisson's ratio in the (001) plane for stretching in the [100] crystallographic direction is only found to be negative up to pressures of similar to 30 GPa, with maximum auxeticity being predicted to occur at similar to 15 GPa. It was also shown that the extent of auxetic behavior may be explained through two mechanisms that act concurrently, namely (i) a mechanism which involves rotations of tetrahedra that project in the (001) plane in the form of rotating semi-rigid squares and (ii) a mechanism, which is being reported for the first time, whereby the tetrahedra deform and become flatter. (C) 2022 Author(s).

Automated summary

The mechanical properties of single crystals boron arsenate, BAsO4, are simulated under various pressures using density functional theory. The results show that the elastic constants and auxeticity are highly dependent on pressure, with maximum auxetic behavior observed at around 15 GPa.