Anomalous Isotopic Effect on the Lattice Parameter of Silicon
2002; American Physical Society; Volume: 89; Issue: 28 Linguagem: Inglês
10.1103/physrevlett.89.285901
ISSN1092-0145
AutoresHans‐Christian Wille, Yuri Shvyd’ko, E. Gerdau, M. Lerche, M. Lucht, H. D. Rüter, J. Zegenhagen,
Tópico(s)X-ray Diffraction in Crystallography
ResumoThe difference Delta(a)=a(30)-a(28) of the lattice parameter of 30Si and 28Si crystals is measured over a temperature range from 4.7 to 700 K. In disagreement with existing knowledge, the strongest isotopic effect is not detected at the lowest achieved temperature T=4.7 K. An anomalous behavior is observed: The relative difference |Delta(a)/a| attains its maximum value of 56.8(5) ppm at T=75(10) K. The anomalous behavior is attributed to the influence of phonon modes with negative Grüneisen parameters. At T=700 K the effect still amounts to 30% of the maximal value. The experimental data are consistent with an approach based on the density-functional perturbation theory.
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