LAUSR

Abstract H2O ice is known to exist as a number of different polymorphs. One such polymorph is ice X, a symmetrical phase of ice which is known to be stable at high pressures and low temperatures. In this work, the mechanical properties of ice X have been studied through DFT simulations, and it has been shown that ice X has the potential to exhibit auxetic behaviour (negative Poisson's ratio) at 45° off-axis in the (100), (010) and (001) planes. Studying the deformation of two orthogonally interconnected rhombi has shown that this predicted negative Poisson's ratio can be attributed to the interplay between distortion and hinging of these rhombi. Moreover, it has been shown that the auxetic potential of ice X increases with an increase in hydrostatic pressure, which behaviour is explained by the rhombi approaching quasi-perfect behaviour resulting in a decrease in the distortion of the rhombi and an increase in hinging mechanism.