Boron-implantation-induced crystalline-to-amorphous transition in nickel: An experimental assessment of the generalized Lindemann melting criterion

The generalized Lindemann melting hypothesis has recently been used to deve lop a unified thermodynamic criterion for melting applicable to both heat-i nduced melting and disorder-induced crystalline-to-amorphous (c-a) transfor mation. The hypothesis stipulates that the sum [mu(2)](Total) of the static and dynamic root-mean-square (rms) atomic displacements is a constant frac tion of the nearest-neighbor distance along the melting curve of a solid. T o test this hypothesis, energy-filtered selected area electron-diffraction intensity measurements were used to determine the generalized Lindemann par ameter delta= root[mu(2)](Total) /d(nn), in which d(nn) represents the near est-neighbor distance, as a function of boron concentration during implanta tion of 50-keV B+ into polycrystalline Ni at 77 K. The onset of amorphizati on was found to occur close to 10 at. % boron, which is in good agreement w ith the value predicted by T-o curve calculated using the generalized Linde mann hypothesis. Moreover, the critical value of the generalized Lindemann parameter for amorphization, delta(Critical) =0.115+/-0.01, is within exper imental error, identical to that for Ni just below its thermodynamic meltin g temperature of T=1728 K, hence providing a direct confirmation for the ge neralized Lindemann melting hypothesis.