Experimental and Theoretical Investigation of the Elastic Moduli of Silicate Glasses and Crystals
Experimental and Theoretical Investigation of the Elastic Moduli of Silicate Glasses and Crystals
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DOI：
10.3389/fmats.2017.00002
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发表时间：
2017-02
影响因子：
3.2
通讯作者：
Katharina Philipps;R. Stoffel;R. Dronskowski;R. Conradt
中科院分区：
文献类型：
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作者：
Katharina Philipps;R. Stoffel;R. Dronskowski;R. Conradt
本文提出了一种结合量子力学和热力学的方法来研究多组分硅酸盐玻璃的力学性质。基于密度泛函理论（DFT）对各种硅酸盐体系进行了量子化学计算，以探索给定化学组成下存在的结晶多晶型物。这些计算再现了已知多晶型物的性质，即使在具有广泛多晶型的系统中，如MgSiO 3。依赖于原子和电子结构的性质，即，正确预测了摩尔体积（密度）和体积模量。理论数据（摩尔平衡体积，体积模量），然后用来补充现有的实验数据。在一个唯象的评估，实验数据的体积模量，宏观性质上的声子结构，被发现线性比例与原子空间需求的比例，以普遍的方式实际摩尔体积。从高压多晶型到玻璃的硅酸盐由单一主线表示。这表明，在德拜极限以上（实际上：在室温以上），弹性波探测短程有序配位多面体和它们的下一个邻居链接，而存在或不存在扩展的平移对称性是无关紧要的。因此，玻璃可以被视为-相对于调查的性质-作为多晶型系列的可结晶成员。二元玻璃与它们的单组分端元非常符合同一条线，同样在结晶态和玻璃态。最后，它表明，多组分玻璃的宏观性质也是线性叠加的性质，其组成相（从相图或热化学计算确定）采取在各自的玻璃态。这通过工业玻璃组合物的热容和杨氏模量的实验得到验证。可以得出结论，结合量子力学和热化学方法是设计具有所需机械性能的玻璃的真正定量方法，例如，用于开发高模量玻璃。
A combined quantum-mechanical and thermodynamic approach to the mechanical properties of multicomponent silicate glasses is presented. Quantum chemical calculations based on density-functional theory (DFT) on various silicate systems were performed to explore the crystalline polymorphs existing for a given chemical composition. These calculations reproduced the properties of known polymorphs even in systems with extensive polymorphism, like MgSiO3. Properties resting on the atomic and electronic structure, i.e., molar volumes (densities) and bulk moduli were predicted correctly. The theoretical data (molar equilibrium volumes, bulk moduli) were then used to complement the available experimental data. In a phenomenological evaluation, experimental data of bulk moduli, a macroscopic property resting on phononic structure, were found to linearly scale with the ratios of atomic space demand to actual molar volume in a universal way. Silicates ranging from high-pressure polymorphs to glasses were represented by a single master line. This suggests that above the Debye limit (in practice: above room temperature), the elastic waves probe the short range order coordination polyhedra and their next-neighbor linkage only, while the presence or absence of an extended translational symmetry is irrelevant. As a result, glasses can be treated – with respect to the properties investigated – as commensurable members of polymorphic series. Binary glasses fit the very same line as their one-component end-members, again both in the crystalline and glassy state. Finally, it is shown that the macroscopic properties of multicomponent glasses also are linear superpositions of the properties of their constitutional phases (as determined from phase diagrams or by thermochemical calculations) taken in their respective glassy states. This is verified experimentally for heat capacities and Young’s moduli of industrial glass compositions. It can be concluded, that the combined quantum mechanical and thermochemical approach is a truly quantitative approach for the design of glasses with desired mechanical properties, e.g., for the development of high-modulus glasses.