Effect of impurities on the ideal tensile strength of covalent crystals - ab-initio quantum molecular dynamics calculations

Using first-principles electronic structure calculations in the local density approximation combined with lattice dynamics, we investigate the effect of III/V impurities on the ideal strength of covalent solids (C, Si, and Ge). Our results show that undoped crystalline solids are stronger in tension along [111] than n-type crystalline solids. P doping has a negligible effect on ideal tensile strength, while n-type doping causes a small reduction in strength of about 6%. The n-type impurity effect is due to the negative (repulsive) contribution from the bottom state of the distorted conduction band to the ideal strength of the solid.