First-principles study on the dilute Si in bcc Fe: Electronic and elastic properties up to 12.5 at.%Si

In order to understand the effect of Si on various properties in bcc Fe, first-principles calculations are employed to investigate the elastic, electronic, and bond characteristic of Fe-Si system with the main focus on dilute Si up to 12.5 at.%Si concentrations based on electronic structure calculations. The stress-strain method for elasticity are performed to obtain the elastic constants of dilute Si in bcc Fe at 0, 2.4, 5.6, 8.3, 10.9, and 12.5 at.%Si. The calculated elastic properties show significantly change beyond 8.3 at.%Si. The bulk to shear modulus ratio indicate the ductile to brittle transition as the Si content increases beyond 8.3 at.%. Electronic density of states, local magnetic moment, and force constants results indicate different Fe-Si bond characteristic between above and below 8.3 at.%Si concentrations which can be taken as the combined effect of the magnetic property and the ordering tendency from bcc solid solution to partial ordering of D0₃ around 10.9 at.%Si.