Past exam of the condensed matter physics course of the University of Oxford 2019 2 f Solution 2026-10-25
Square the stated Lindemann melting criterion and insert the high-temperature displacement:Thus, with ,Here , so the use of the high-temperature approximation is only moderately justified. It is an estimate, not a controlled limit. Retaining the exact Einstein mean-square displacement in the same heuristic criterion gives about , indicating the size of that particular correction. The empirical threshold and the independent-oscillator model introduce additional uncertainty.