Molecular Simulation of Covalent Bond Dynamics in Liquid Silicon

Abstract

Many atomic liquids can form transient covalent bonds reminiscent of those in the corresponding solid states. These directional interactions dictate many important properties of the liquid state, necessitating a quantitative, atomic-scale understanding of bonding in these complex systems. A prototypical example is liquid silicon, wherein transient covalent bonds give rise to local tetrahedral order and consequent non-trivial effects on liquid state thermodynamics and dynamics. To further understand covalent bonding in liquid silicon, and similar liquids, we present an ab initio simulation-based approach for quantifying the structure and dynamics of covalent bonds in condensed phases. Through the examination of structural correlations among silicon nuclei and maximally localized Wannier function centers, we develop a geometric criterion for covalent bonds in liquid Si. We use this to monitor the dynamics of transient covalent bonding in the liquid state and estimate a covalent bond lifetime. We compare covalent bond dynamics to other processes in liquid Si and similar liquids and suggest experiments to measure the covalent bond lifetime.

Observation of plasmon excitation in liquid silicon by inelastic x-ray scattering

“…The fraction of pairs and the fraction x we introduced here are not directly coincident quantities, but the value of x we derived is not necessarily irrelevant from such picture. In liquid Si, the observed plasmon energy is about 17 eV, and the oscillation period is approximately 0.2 fs that is much shorter than the lifetime of the transient covalent bonding ≈600 fs [24]. Plasma oscillates ≈3000 times during such bond lifetime, and for plasma oscillations, such dynamical bondformation appears almost frozen.…”

“…The observation of contour maps of valence electron density revealed charge accumulation and annihilation between pairs of atoms, which was interpreted as transient covalent bonds. A recent ab initio MD simulations provides a quantitative evaluation of the lifetime of the covalent bond and reported the value of ≈600 fs [24]. On the other hand, it was argued that the transient accumulation of valence electrons between ions was observed in the simulation but not necessarily due to covalent bonding, with the analysis using the orbital free ab initio simulation [15].…”

Approximately 30 nm Nanogroove Formation on Single Crystalline Silicon Surface under Pulsed Nanosecond Laser Irradiation

“…However, the reported research demonstrates that for the liquid silicon, the contributions of the covalent bond pairs, diffuse pairs, and lone pairs are estimated to be about 17%, 83%, and less than 1%, respectively. 34 The covalent bonds in liquid Si rapidly break due to the thermal fluctuation and rebond on subpicosecond time scales. The covalent bond lifetime in the liquid Si is τ ≈ 0.6 ps.…”

Self-healing Materials: A Review of Recent Developments

“…When a coordination bond is formed, it is no different from a common covalent bond, except that the two electrons shared between the bonding atoms do not come from one atom, but from the other, and the metal coordination bond is the ligand and metal atoms or ions formed by the coordination bond. [67] Metal Coordination Bond also has the characteristics of covalent bond: directivity and saturation, [68] at the same time, metal coordination bond has certain conductivity [69] to make it more widely used. In recent years, it has been widely used in the field of self-healing to improve the performance of selfhealing materials, so that the materials have better self-healing performance, [70][71][72] preeminent electrical conductivity.…”