Molecular dynamics study of anisotropic shock responses in oriented α-quartz single crystal

• Published in: Journal of materials science 2022-03, Vol.57 (12), p.6688-6705
• Main Authors: Zhang, Huadian, Shukla, Manoj K., Larson, Steve, Rajendran, A. M., Jiang, Shan
• Format: Article
• Language: English
• Subjects: Amorphous structure; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Computation & Theory; Crystal structure; Crystallography; Crystallography and Scattering Methods; Deformation; Distribution functions; Elastic limit; Energy absorption; Hugoniot curves; Impact velocity; Materials Science; Mechanical properties; Molecular dynamics; Monoclinic lattice; Polymer Sciences; Precursors; Propagation; Quartz crystals; Radial distribution; Shear strain; Shock wave propagation; Simulation; Single crystals; Sliding; Solid Mechanics; Strain rate; Stress distribution; Temperature distribution; Thermodynamic properties; Velocity
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-022-07076-0

This paper presents an investigation aimed at understanding the shock wave propagation response of oriented α-quartz single crystals by using molecular dynamics (MD) simulations. Several orthorhombic unit cells with different crystal orientations converted from an original monoclinic α-quartz crystal were used to construct the supercells with the crystallographic orientations of [100], [120], and [001] aligned with the shock direction. The shock wave propagation responses were analyzed via position-time ( x–t ) diagrams of several thermal and mechanical properties. Atomic shear strain and radial distribution function (RDF) were used to investigate the shock-induced material deformation and phase change from crystal to disordered fluid-like flow. The MD simulations enabled the construct of the shock Hugoniot, in terms of the shock velocity U s versus the impact/particle speed U p (i.e., U s –U p plane), and the Hugoniot elastic limit σ HEL response with reference to precursor decay. It was found that the single crystal α-quartz sample exhibits noticeable anisotropic behaviors in terms of kinetic temperature distribution, stress distribution, and Hugoniot shock velocity response. Among the three studied crystal directions at a relatively low U p , the [120] sample showed a non-uniform shock-induced deformation pattern, and the [001] crystal showed the most prominent energy absorption capacity. At a given high impact speed (e.g., U p  = 2.5 km/s), the [001] sample showed a relatively longer amorphous shocked region followed by a shorter deformed crystal region, which was very different from the compressed regions behind the shock front in the other two samples. For all oriented crystals, the RDF results predicted an amorphous structure of silica emerging in the compressed region at the higher speed impact, in addition to a few “shear-bands” or crystal sliding in the [120] sample. The shock Hugoniot U s –U p also indicated a noticeable anisotropic behavior of the α-quartz. At a given value of U p above 1.5 km/s, the [001] crystal yielded the largest U s while the [120] crystal yielded the smallest. A “two-wave” structure was evidently found in the [001] sample at U p  = 2.5 km/s, while such a structure was not clearly seen for the other two orientations. The precursor decay phenomenon was observed in [001] direction, indicating a strong strain rate effect on σ HEL ; however, the σ HEL decay was not easy to identify in [100] and [120] directions due to the inst