First-principles calculation of intrinsic defect formation volumes in silicon

TL;DR

This study uses first-principles calculations to analyze how pressure affects defect formation volumes in silicon, revealing significant variations and anisotropic relaxations around defects.

Contribution

It provides detailed pressure-dependent formation enthalpies and volumes for all known vacancy and self-interstitial configurations in silicon, including charge state effects.

Findings

Neutral vacancy has a formation volume that varies with pressure.

Zero-pressure formation volume of a Frenkel pair is notably negative.

Lattice relaxation around neutral defects is highly anisotropic.

Abstract

We present an extensive first-principles study of the pressure dependence of the formation enthalpies of all the know vacancy and self-interstitial configurations in silicon, in each charge state from -2 through +2. The neutral vacancy is found to have a formation volume that varies markedly with pressure, leading to a remarkably large negative value (-0.68 atomic volumes) for the zero-pressure formation volume of a Frenkel pair (V + I). The interaction of volume and charge was examined, leading to pressure--Fermi level stability diagrams of the defects. Finally, we quantify the anisotropic nature of the lattice relaxation around the neutral defects.