Molecular Dynamics Simulations of Structural and Mechanical Properties in MgSiO₃ Glass

Molecular dynamics simulations of MgSiO₃ glass have been carried out to study the structural and mechanical properties under uniaxial tension. The network structure consists of SiO_x and MgO_y units which link to others by corner-, edge-, and face-sharing bonds. The Si-rich and Mg-rich regions exist in MgSiO₃ glass. The stress–strain curves exhibit the elastic and plastic characteristics at the various strain rates. The transformations of SiO_x and MgO_y units occur with increasing strain, at which the corner-, edge- and face-sharing bonds among SiO_x and MgO_y units change. The Si-rich and Mg-rich regions increase with increasing strain. Not only the Mg–O bond length is easier to stretch than the Si–O bond length but also the O–Mg–O bond angle of MgO_y units is easier to vary than that of SiO_x units with the strain. The porosity is analyzed via the voids. The voids gather into the clusters of voids. The radii of voids increase with increasing strain. The number of big Mg-voids increases under the tension and these voids coalesce to form large pores. These large pores do not coalesce to cause the fractured free surfaces. The formation of shear band was observed at the strain of 0.82.