Computing Elastic Tensors of Amorphous Materials from First-Principles

TL;DR

This paper presents a new computational method using Density Functional Theory to accurately determine the elastic tensors of amorphous materials, addressing challenges posed by their structural disorder and non-affine transformations.

Contribution

The study introduces a novel approach for calculating elastic tensors of amorphous materials, applicable to both bulk and thin films, accounting for their inherent disorder and boundary effects.

Findings

Method aligns with classical Young's modulus measurements.

Applicable to both bulk and ultra-thin amorphous films.

Enables better understanding of mechanical properties in amorphous materials.

Abstract

Advancements in modern semiconductor devices increasingly depend on the utilization of amorphous materials and the reduction of material thickness, pushing the boundaries of their physical capabilities. The mechanical properties of these thin layers are critical in determining both the operational efficacy and mechanical integrity of these devices. Unlike bulk crystalline materials, whose calculation techniques are well-established, amorphous materials present a challenge due to the significant variation in atomic topology and their non-affine transformations under external strain. This study introduces a novel method for computing the elastic tensor of amorphous materials, applicable to both bulk and ultra-thin films in the linear elastic regime using Density Functional Theory. We exemplify this method with a-SiO2, a commonly used dielectric. Our approach accounts for the structural disorder inherent in amorphous systems, which, while contributing to remarkable material properties, complicates traditional elastic tensor computation. We propose a solution involving the inability of atomic positions to relax under internal relaxation, near the boundaries of the computational unit cell, ensuring the affine transformations necessary for linear elasticity. This method's efficacy is demonstrated through its alignment with classical Young's modulus measurements, and has potential for broad application in fields such as Technology Computer Aided Design and stress analysis via Raman spectra. The revised technique for assessing the mechanical properties of amorphous materials opens new avenues for exploring their impact on device reliability and functionality.