THEORETICAL TENSILE-STRESS IN TUNGSTEN SINGLE-CRYSTALS BY FULL-POTENTIAL FIRST-PRINCIPLES CALCULATIONS

Fully self-consistent ab initio electronic structure calculation of th eoretical tensile strength is performed for the first time using full- potential LAPW method. As a specific example, tensile strength of sing le-crystalline tungsten loaded uniaxially along the (001) and (111) di rections is analyzed. Although tungsten is elastically nearly isotropi c (C-44 approximate to C'), theoretical tensile strength exhibits a ma rked anisotropy (sigma(001)(th) = 0.289 Mbar, sigma(111)(th) = 0.401 M bar). This anisotropy is explained in terms of structural energy diffe rences between bcc, fee and simple cubic structures which occur on the calculated deformation paths. Theoretical results compare favorably w ith experimental value of 0.247 +/- 0.036 Mbar obtained for tungsten w hiskers grown along the (110) direction. (C) 1997 Elsevier Science S.A .