Contribution of stacking fault in lowering the theoretical density of nickel

• The presence of stacking fault (SF) changes the density of metals and alloys.
• First-principle calculations show reduction in the density of Ni due to SF.
• Conventionally measured SFE is higher than that of the SFE with relaxation.
• Defect-structure should be relaxed to calculate dimensions and energy correctly.

It has been shown with the help of first-principle based calculations that the occurrence of stacking fault (SF) changes the density of nickel. Calculations, based upon a twelve {1 1 1}-plane supercell of face-centered-cubic (fcc) nickel show that the stacking fault energy in the case of “conventional” stacking is higher by ∼2 mJ/m2 than that of the supercell having an appropriate dilation along the fault-plane normal. The {1 1 1}-type stacking fault energy of fcc-Ni, 136.683 mJ/m2, has been calculated using 4.09746 × 105 mm2/mm3 SF density, which has resulted in the decrease in the bulk density of fcc-Ni by 0.0895%. This approach of relaxation of a structure with stacking faults along the plane normal may be extended to calculate more accurate generalized stacking fault and to measure the lattice distortion due to various values of defect-densities.