# The Effect of the Chemical Composition on Mechanical Properties of CMAS Diopside Glass Ceramics
## 3 Results and Discussion  
### Effect of the Nanocrystal  
To identify mechanical property differences between GCs' influence and their counterpart pure glass or pure crystal materials, uniaxial tension was applied on these three samples (as shown in Figure 2). Figure 2a shows the stress-strain curves for the three samples. The results are consistent with common sense, in which the ceramic crystal materials are significantly stronger than their glass material counterparts and the strength of the corresponding GCs lies in the middle. In addition, it is obvious that the stress for diopside crystalline samples drops sharply to zero at about 0.13 strain, while the other two samples still show a high and even a strain-hardening flow stress. The corresponding atomistic structure for the diopside crystalline sample is shown in Figure 2c. It is clear that the fracture takes place in the crystal. No fracture or small void exists based on Figure 2b,d. These results reveal that with the nanocrystal embedded in the glass, the strength is enhanced while ductility remains. They also echo the previous experimental results [33], which verify the reliability of the MD simulation.  
Taking advantage of the atomistic simulation, the Vomis shear strain for each ion was calculated and colored based on its value, as shown in Figure 2b,c, where a red color indicates significant shear deformation. For the pure crystalline diopside sample, the high shear strain ions were concentrated at the fracture surface. For the glass sample, some areas  
Figure 2: (**a**) Stress–strain curves for CMS glass, CMS diopside and CMS diopside GC samples under tensile stress; (**b**) contour plots of shear strain for glass sample at 0.18 strain; (**c**) contour plots of shear strain for diopside sample at 0.13 strain; (**d**) contour plots of shear strain for CMS diopside GCs sample at 0.18 strain. Each ion is colored according to its shear strain.  
are blue and some areas are yellow with red, indicating that the shear strain distribution is not homogeneous. It is worthwhile to mention that there is no significant high shear strain local region, which indicates that the sample is not at risk of fracture for the time being. For the diopside GCs sample, we can see that the shear strain distribution has a certain pattern, in which the ions surrounding the diopside nanocrystal are all subjected to a relatively high shear strain, while the ions in the nanocrystal are in a low shear-strain state. These findings reveal that nearly all the deformation takes place in the glass region and tends to concentrate in the region around the nanocrystal.  
To clearly inspect the deformation pattern, we calculated the displacement vector magnitude for each ion. The homogenous cell deformations were not included in the calculation, so displacements were contributed by inelastic deformation and affected the mechanical properties of materials. As shown in Figure 3, the ions for the glass sample and diopside GCs sample are colored based on their displacement vector magnitude. On the one hand, we can see that the displacement in the glass sample followed certain bands, as shown in Figure 3a, so future fracture may take place in this region. On the other hand, the region near the top and left side of the nanocrystal has severe displacement, whose magnitude is larger than that of the glass sample. As a result, we can expect that future fracture may occur at the interface and earlier than that in pure glass sample.