Surface Vibration Modes in Monatomic Body-Centered Cubic Crystals:The (001) Surface.

摘要

Surface vibration modes for the (001) surface of monatomic bcc crystals are examined using a simple model which allows for full cubic anisotropy and which exactly fits the second-order elastic constants. For both the semi-infinite crystal and the crystal slab approaches,the effect of anisotropy is examined for iron,vanadium and isotropic tungsten. For each crystal a surface mode with shear-horizontal (SH) polarization is found below the SH bulkband along the (100) direction but not along the (110) direction. For long wavelength,the frequency of this surface mode departs from the bulk band edge as the inverse cube of wavelength and the localization depth is proportional to the inverse square of wavelength. A surface mode with SH polarization is found above the SH bulkband in both the (100) and (110) directions for vanadium. In addition to the Rayleigh waves, a number of short wavelength surface modes with sagittal-plane polarization are found for each crystal. (Modified author abstract)