Liquid-liquid Phase transitions in silicon

TL;DR

This paper investigates liquid-liquid phase transitions in supercooled and warm-dense silicon using DFT-based simulations, revealing multiple transitions driven by ionization and electron scattering effects.

Contribution

It introduces a computational approach combining neutral pseudo-atom DFT and MD to identify and analyze liquid-liquid phase transitions in silicon under various conditions.

Findings

Identification of an ionization-driven phase transition.

Discovery of three liquid-liquid phase transitions including a known one.

Robustness of LPTs up to 1 eV and detailed characterization of properties.

Abstract

We use computationally simple neutral pseudo-atom (`average atom') one-center density functional theory (DFT) and standard N-center DFT-Molecular Dynamics simulations to elucidate liquid-liquid phase transitions (LPTs) in supercooled liquid silicon at 1200K ,and also in silicon under warm-dense matter conditions up to 11604k (1 eV). An ionization-driven transition and three LPTs including the known LPT near 2.5 g/cm$^3$ are found. They are robust even to 1 eV. The pair distributions functions, pair potentials, electrical conductivities, and compressibilites are reported. The LPTs are elucidated within a Fermi liquid picture of electron scattering at the Fermi energy that complements the usual transient covalent bonding picture.