The ideal strength of tungsten
The ideal strength of tungsten
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DOI：
10.1080/01418610010007902
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发表时间：
2001-07-01
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影响因子：
--
通讯作者：
Morris, JW
中科院分区：
文献类型：
--
作者：
Roundy, D;Krenn, CR;Morris, JW
在局域密度近似下，利用赝势密度泛函理论，计算了W在{110}、{112}和{123}面上滑移时的理想剪切强度，并考虑了垂直于外加剪切的完全结构松弛。所有平面上弱方向的强度几乎相等(约18 Gpa，或剪切模数G的11%)。此外，剪切失稳发生在大致相同的外加剪切应变(17-18%)。这种不同寻常的各向同性可以用剪切过程中达到的高能鞍点的原子构型来解释。对这些鞍点的分析还可以简单地解释在体心立方金属中含有&111&>方向的平面上位错的铅笔滑移现象。最后，我们计算了W在{100}上的理想解理强度，并将我们计算的理想剪切强度和解理强度与实验的纳米压痕和晶须测量进行了比较。所有这些结果都可以用Frenkel-Orowan结晶学模型相当简单地理解。
Using pseudopotential density functional theory within the local-density approximation, we calculate the ideal shear strengths of W for slip on {110}, {112} and {123} planes allowing for complete structural relaxation orthogonal 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 applied shear strain (17-18%). This unusual isotropy is explained in terms of the atomic configuration of high-energy saddle points reached during shear. Analysis of these saddle points may also offer a simple explanation for the prevalence 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 strengths with experimental nanoindentation and whisker measurements. All these results can be rather simply understood using a Frenkel-Orowan crystallographic mode.