Deformation of phyllosilicate can control the dynamics of the Earth’s crust. The phenomenological relationship between stress and deformation is known for some typical phyllosilicates; however, the underlying physics originating from the crystal structures is poorly understood. In this study, the deformation mechanism of pyrophyllite along basal planes was revealed through density functional theory calculations and atomic-scale theory of friction. The stable and metastable interlayer structures formed by interlayer slide were consistent with the experimental results reported previously by highresolution transmission electron microscopy. The difference in potential energies between stable and metastable interlayer structures can be interpreted as the difference in the stacking of dioctahedral sheets between the adjacent layers. The estimated friction coefficient of the pyrophyllite between adjacent layers was consistent with the results of atomic force microscopy, suggesting that atomic-scale friction can be adequately estimated by this method. The calculated shear stress in our simulations has a linear relationship with the normal stress and has no significant crystallographic dependence on sliding direction along the basal planes. The crystallographic isotropy of interlayer friction is explained by the absence of interlayer cations in pyrophyllite, while muscovite showed crystallographic anisotropy as observed in previous studies. The macroscopic friction of a single crystal of pyrophyllite was estimated from atomic-scale friction by using the area of contact. The macroscopic friction coefficient of ideal interlayer sliding was estimated to be 0.134, which was smaller than a reported value (0.276) in shear experiments conducted for wet polycrystalline gouge layers. This difference can be primarily explained by the degree of orientation of pyrophyllite particles in the gouge layers. The friction coefficient estimated by a simple model of randomly oriented pyrophyllite gouge layer was 0.203 ± 0.001, which was similar to the reported value of 0.276 and clearly smaller than the values (0.6–0.85) of common minerals estimated by the empirical Byerlee’s law. These results indicate that weak interlayer friction of phyllosilicates has a large effect on the low frictional strength of gouge layers in natural faults. Our methodology and results are useful for understanding the physics behind the phenomenological friction laws of phyllosilicate gouge.

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叶蜡石的层间能量：对宏观摩擦的影响

层状硅酸盐的变形可以控制地壳的动力学。对于一些典型的页硅酸盐，应力和变形之间的现象学关系是已知的；然而，人们对源自晶体结构的基础物理学知之甚少。本研究通过密度泛函理论计算和原子尺度摩擦理论揭示了叶蜡石沿基面的变形机制。夹层滑动形成的稳定和亚稳态夹层结构与高分辨率透射电子显微镜先前报道的实验结果一致。稳定和亚稳态层间结构之间的势能差异可以解释为相邻层之间二八面体片堆叠的差异。相邻层间叶蜡石的估计摩擦系数与原子力显微镜的结果一致，表明该方法可以充分估计原子级摩擦。在我们的模拟中计算出的剪应力与法向应力呈线性关系，并且对沿基面的滑动方向没有显着的晶体学依赖性。层间摩擦的结晶各向同性可以通过叶蜡石中不存在层间阳离子来解释，而白云母显示出如先前研究中观察到的结晶各向异性。叶蜡石单晶的宏观摩擦是通过使用接触面积从原子级摩擦来估计的。理想层间滑动的宏观摩擦系数估计为0.134，在对湿多晶凿岩层进行的剪切实验中，该值小于报告值 (0.276)。这种差异主要可以用凿层中叶蜡石颗粒的取向程度来解释。由随机取向的叶蜡石凿层的简单模型估计的摩擦系数为 0.203 ± 0.001，与报告值 0.276 相似，明显小于经验拜尔利定律估计的常见矿物值 (0.6-0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。276）在对湿多晶凿层进行的剪切实验中。这种差异主要可以用凿层中叶蜡石颗粒的取向程度来解释。由随机取向的叶蜡石凿层的简单模型估计的摩擦系数为 0.203 ± 0.001，与报告值 0.276 相似，明显小于经验拜尔利定律估计的常见矿物值 (0.6-0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。276）在对湿多晶凿层进行的剪切实验中。这种差异主要可以用凿层中叶蜡石颗粒的取向程度来解释。由随机取向的叶蜡石凿层的简单模型估计的摩擦系数为 0.203 ± 0.001，与报告值 0.276 相似，明显小于经验拜尔利定律估计的常见矿物值 (0.6-0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。这种差异主要可以用凿层中叶蜡石颗粒的取向程度来解释。由随机取向的叶蜡石凿层的简单模型估计的摩擦系数为 0.203 ± 0.001，与报告值 0.276 相似，明显小于经验拜尔利定律估计的常见矿物值 (0.6-0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。这种差异主要可以用凿层中叶蜡石颗粒的取向程度来解释。由随机取向的叶蜡石凿层的简单模型估计的摩擦系数为 0.203 ± 0.001，与报告值 0.276 相似，明显小于经验拜尔利定律估计的常见矿物值 (0.6-0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。203 ± 0.001，与报告值 0.276 相似，明显小于由经验拜尔利定律估计的常见矿物的值 (0.6–0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。203 ± 0.001，与报告值 0.276 相似，明显小于由经验拜尔利定律估计的常见矿物的值 (0.6–0.85)。这些结果表明，页硅酸盐的弱层间摩擦对天然断层中凿层的低摩擦强度有很大影响。我们的方法和结果有助于理解层状硅酸盐凿岩现象摩擦定律背后的物理原理。