Molecular Origins of Deformation in Amorphous Methane Hydrates

Water and methane can stay together under low temperature and high pressure in the forms of liquid solutions and crystalline solids. From liquid and gaseous states to crystalline solids or the contrary processes, amorphous methane hydrates can occur in these evolution scenarios. Herein, mechanical properties of amorphous methane hydrates are explored for the first time to bridge the gap between mechanical responses of monocrystalline and polycrystalline methane hydrates. Our results demonstrate that mechanical properties of amorphous methane hydrates are strongly governed by our original proposed order parameter, namely, normalized hydrogen-bond directional order parameter. Followed by this important achievement, a multistep deformation mechanism core is proposed to explain mechanical properties of amorphous methane hydrates. Through an extensive detailed analysis of amorphous methane hydrates, our simulation results not only greatly enlarge our fundamental understanding for mechanical responses of amorphous methane hydrates in geological systems but also offer a fresh perspective in structure-property topics of solid materials in future science and technology.