The ideal strength of tungsten

Citation
D. Roundy et al., The ideal strength of tungsten, PHIL MAG A, 81(7), 2001, pp. 1725-1747
Citations number
40
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS ANDMECHANICAL PROPERTIES
ISSN journal
13642804 → ACNP
Volume
81
Issue
7
Year of publication
2001
Pages
1725 - 1747
Database
ISI
SICI code
1364-2804(200107)81:7<1725:TISOT>2.0.ZU;2-U
Abstract
Using pseudopotential density functional theory within the local-density ap proximation, we calculate the ideal shear strengths of W for slip on {110}, {112} and {123} planes allowing for complete structural relaxation orthogo nal to the applied shear. The strengths in the weak direction on all planes are found to very nearly equal (about 18 GPa, or 11% of the shear modulus G). Moreover, the shear instability occurs at approximately the same applie d shear strain (17-18%). This unusual isotropy is explained in terms of the atomic configuration of high-energy saddle points reached during shear. An alysis of these saddle points may also offer a simple explanation for the p revalence of the pencil glide of dislocation on planes containing a < 111 > direction in bcc metals. Finally, we calculate the ideal cleavage strength of W on {100} and compare our calculated ideal shear and cleavage strength s with experimental nanoindentation and whisker measurements. All these res ults can be rather simply understood using a Frenkel-Orowan crystallographi c mode.