Dislocations are the primary carriers of plasticity in metallic material. Understanding the basic mechanisms for dislocation movement is paramount to predicting the material mechanical response. Relying on atomistic simulations, we observe a transition from non-Arrhenius to Arrhenius behavior in the rate for an edge dislocation to overcome the elastic interaction with a prismatic loop in tungsten. Beyond the critical resolved shear stress, the process shows a non-Arrhenius behavior at low temperatures. However, as the temperature increases, the activation entropy starts to dominate, leading to a traditional Arrhenius behavior. We have computed the activation entropy analytically along the minimum energy path following Schoeck's methods [1], which capture the cross-over between anti-Arrhenius and Arrhenius domains. Also, the Projected Average Force Integrator (PAFI) [2], another simulation method to compute free energies along an initial transition path, exhibits considerable concurrence with Schoeck's formalism. We conclude that entropic effects need to be considered to understand processes involving dislocations bypassing elastic barriers close to the critical resolved shear stress. More work needs to be performed to fully understand the discrepancies between Schoeck's and PAFI results compared to molecular dynamics.

翻译：位错是金属材料中塑性变形的主要载体。理解位错运动的基本机制对于预测材料的力学响应至关重要。基于原子模拟，我们观察到钨中刃型位错克服与棱柱环弹性相互作用的速率存在从非Arrhenius到Arrhenius行为的转变。在临界分切应力之上，该过程在低温下表现为非Arrhenius行为。然而，随着温度升高，激活熵开始主导，导致传统的Arrhenius行为。我们依据Schoeck方法[1]沿最小能量路径解析计算了激活熵，该方法捕捉了反Arrhenius与Arrhenius区域之间的交叉。同时，投影平均力积分器(PAFI)[2]——另一种沿初始转变路径计算自由能的模拟方法——与Schoeck形式表现出显著的一致性。我们得出结论：需考虑熵效应以理解涉及位错绕过接近临界分切应力的弹性障碍的过程。针对Schoeck方法与PAFI结果相较于分子动力学存在的差异，仍需开展进一步研究以全面揭示其机理。