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He⁺-ion backscattering studies on the clean W(110) surface at 300 K show that there is less than 2% change in the first interplanar spacing for the clean surface. There is however a large anisotropy in the thermal vibration amplitude for the surface atoms with the component normal to the surface 2.6 times larger than the one-dimensional bulk amplitude while the parallel component in the surface plane shows very little enhancement.
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Smith et al. (1987) studied this question.
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