Abstract:
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We perform calculations of the momentum distribution n(k) in solid 4He by means of path integral Monte Carlo methods.We see that, in perfect crystals, n(k)does not depend on temperature T and that is different from the classical Gaussian
shape of the Maxwell-Boltzmann distribution, even though these discrepancies decrease
when the density of the system increases. In crystals presenting vacancies, we see that for T ≥ 0.75 K, n(k) presents the same behavior as in the perfect crystal, but,
at lower T , it presents a peak when k→0. |