Predicting the densities of amorphous materials through first-principles calculations*

First-principles calculations had not ever been performed to predict the densities of amorphous materials. This was due to the fact that because of the disordered nature of amorphous materials, their atomic configurations are completely different from one sample to another, and thus there is no one-to-one correspondence between the densities and the total energies. In preceding reports, in which the densities of amorphous semiconductors were estimated using (semi-) classical molecular dynamics simulations [1], such correspondence was not considered. In our study, to remedy this problem, we have devised a novel method which employs the density functional theory (DFT) and the Car-Parrinello molecular dynamics method. We have applied it to amorphous silicon and found that the determined density and its bulk modulus are in good agreement with experiments. The presented method is expected to be applied to other amorphous systems, including those that are experimentally undiscovered.

[1] H. Seong and L. J. Lewis, Phys. Rev. B 53, 4408 (1996)
[2] Y. Furukawa and Y.-i. Matsushita, arXiv:1704.06107 (2017)