Murali P, Ramamurty U, Shenoy Vijay B
Department of Materials Engineering, Indian Institute of Science, Bangalore, India.
J Chem Phys. 2008 Mar 14;128(10):104508. doi: 10.1063/1.2839300.
A possible mechanism of strain accommodation in large deformation of glasses is crystallization; deformation stability is a measure of the resistance of glasses to crystallization. We study the effect of atomic size ratio and atomic stiffness parameter (related to the curvature of the interatomic potential) on deformation stability of binary glasses using molecular static simulations. The deformation stability of a glass is found to increase with increasing atomic size ratio and magnitude of the atomic stiffness, which is proportional to the bulk modulus of the pure crystalline system, as well as the ratio of atomic stiffnesses of constituent atoms. To understand the role of the above parameters on deformation stability, misfit energies of randomly substituted solid solution fcc crystals and glasses are compared for various atomic size ratios and atomic stiffness values. Unlike in fcc solid solution, the misfit energy of binary glasses is found to be insensitive to the atomic size ratio. It is also found that the packing fraction of glasses is insensitive to the atomic size ratio, consistent with the above result. Beyond a critical atomic size ratio, the misfit energy of fcc solid solution exceeds the energy of the glass, thus making the amorphous state completely stable to deformation induced crystallization. Our analysis shows that critical atomic size ratio decreases with increasing atomic stiffness which leads to an increase in the deformation stability of glasses.
玻璃大变形过程中应变调节的一种可能机制是结晶；变形稳定性是衡量玻璃抗结晶能力的指标。我们使用分子静态模拟研究了原子尺寸比和原子刚度参数（与原子间势的曲率相关）对二元玻璃变形稳定性的影响。发现玻璃的变形稳定性随着原子尺寸比和原子刚度大小的增加而提高，原子刚度大小与纯晶体系统的体积模量以及组成原子的原子刚度之比成正比。为了理解上述参数对变形稳定性的作用，我们比较了不同原子尺寸比和原子刚度值下随机取代固溶体面心立方晶体和玻璃的错配能。与面心立方固溶体不同，发现二元玻璃的错配能对原子尺寸比不敏感。还发现玻璃的堆积分数对原子尺寸比不敏感，这与上述结果一致。超过临界原子尺寸比后，面心立方固溶体的错配能超过玻璃的能量，从而使非晶态对变形诱导结晶完全稳定。我们的分析表明，临界原子尺寸比随着原子刚度的增加而减小，这导致玻璃的变形稳定性增加。
