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Purpose The purpose of this paper is to calculate the Hugoniot relations of polyurea; also to investigate the atomic-scale energy change, the related chain conformation evolution and the hydrogen bond dissociation of polyurea under high-speed shock. Design/methodology/approach The atomic-scale simulations are achieved by molecular dynamics (MD). Both non-equilibrium MD and multi-scale shock technique are used to simulate the high-speed shock. The energy dissipation is theoretically derived by the thermodynamic and the Hugoniot relations. The distributions of bond length, angle and dihedral angle are used to characterize the chain conformation evolution. The hydrogen bonds are determined by a geometrical criterion. Findings The Hugoniot relations calculated are in good agreement with the experimental data. It is found that under the same impact pressure, polyurea with lower hard segment content has higher energy dissipation during the shock-release process. The primary energy dissipation way is the heat dissipation caused by the increase of kinetic energy. Unlike tensile simulation, the molecular potential increment is mainly divided into the increments of the bond energy, angle energy and dihedral angle energy under shock loading and is mostly stored in the soft segments. The hydrogen bond potential increment only accounts for about 1% of the internal energy increment under high-speed shock. Originality/value The simulation results are meaningful for understanding and evaluating the energy dissipation mechanism of polyurea under shock loading, and could provide a reference for material design.

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In present paper, we perform first principles based on density functional theory to investigate the effect of high pressure on phononic, electronic, elastic and thermodynamic properties of ScSi. It is found that phonon dispersion curve of ScSi has no virtual frequency within a given pressure range from 0 GPa to 35 GPa, indicating that the material is thermodynamically stable. When a given pressure is larger than 40 GPa, ScSi is thermodynamically instable and will occurs phase transition. Band structure and density of states confirm that ScSi is metallic. The elastic constant Cij increases with increasing pressure, and meets the Born�s criterion, which shows that ScSi possesses mechanical stability. Meanwhile, the ductility and toughness of material increase with increasing pressure, which is very conducive to industrial applications. In addition, Debye temperature and sound velocity increase linearly with pressures, indicating that appropriate pressure can improve elasticity, hardness, melting point and specific heat.