Tight-binding calculations of stacking energies and twinnability in fcc metals
Tight-binding calculations of stacking energies and twinnability in fcc metals
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DOI：
10.1103/physrevb.69.094116
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发表时间：
2004-03-01
影响因子：
3.7
通讯作者：
Tadmor, EB
中科院分区：
文献类型：
--
作者：
Bernstein, N;Tadmor, EB
我们计算了评估面心立方(FCC)金属通过形成结晶学孪晶而不是位错介导的滑移来塑性变形的趋势所需的材料性质。我们把这种性质称为金属的孪生性。我们使用由连续介质力学与原子性应力-滑移关系耦合而来的孪生性公式。评价孪晶性的基本参数是可由实验测量的弹性常数和面心立方(111)面的各种堆积顺序的能量。这些堆积序列包括本征的堆错组态，以及只能通过计算确定的不稳定堆积能量组态和不稳定孪生能量组态。我们用紧束缚模型计算了8种面心立方金属的必要堆积能、非本征堆积错能和孪晶界能。紧束缚参数的准确性是通过将它们与通过广泛研究文献获得的第一原理值进行比较来确定的。文献调查的结果被包括在论文中，作为读者的资源。结果表明，这些金属的孪晶排列顺序与已有的实验结果一致。我们再现了Al中形变孪生的低发生率，并用孪晶性表达式的近似用材料参数解释了这一现象。我们还预测，还没有实验研究的Pd应该像铜一样容易孪生。
We calculate the material properties needed to evaluate the tendency of a face-centered-cubic (fcc) metal to plastically deform by forming crystallographic twins as opposed to dislocation-mediated slip. We refer to this property as the twinnability of the metal. We use a formulation for twinnability derived from a coupling of continuum mechanics with an atomistic stress-slip relation. The essential quantities for evaluating the twinnability are elastic constants, which are measurable experimentally, and energies for various stacking sequences of the fcc (111) planes. These stacking sequences include the intrinsic stacking fault configuration as well as the unstable-stacking energy and unstable-twinning energy configurations which can only be determined computationally. We use a tight-binding model to evaluate the necessary stacking energies, as well as the extrinsic stacking fault energy and twin-boundary energy, for eight fcc metals. The accuracy of the tight-binding parameters is established by comparing them with first-principles values obtained through an extensive study of the literature. The results of the literature survey are included in the paper as a resource for the reader. We show that the ranking of these metals in order of twinnability agrees with available experimental results. We reproduce the low incidence of deformation twinning in Al, and explain it in terms of the material parameters using an approximation to the twinnability expression. We also predict that Pd, which has not been studied experimentally, should twin as easily as Cu.