Ab Initio and Molecular Dynamics-Based Pair Potentials for Lanthanum Hexaboride

Abstract

Lanthanum hexaboride (LaB 6 ) is a well-known refractory ceramic with unique mechanical and electrochemical behavior, leading to a diverse array of possible attractive applications.In this work, we present and discuss the development of interatomic potentials for LaB 6 using a combination of density functional theory with molecular dynamics simulations. Density functional theory is employed to acquire energetic and dynamic data of the atoms in various configurations and environments. Lattice inversion techniques are then combined with other optimization procedures to yield potentials which can accurately capture the lattice dynamics -mean-square displacements and equilibrium energetics of the system as a function of temperature.

Interatomic pair potentials from DFT and molecular dynamics for Ca, Ba, and Sr hexaborides

“…Details of the perturbations and calculations can be found in Schmidt et al 48 The f B 6 energies are found by expanding the lattice until the variation dE/da has reached a minimal value, and removal of this energy is assumed to produce a cohesive energy dependent upon B-B interO h interactions only, as the intrinsic energy associated with isolated octahedrons is removed.…”

Metal Hexaboride Work Functions: Surface Configurations and the Electrical Double Layer from First‐Principles

“…5 In addition to the stability of these materials, many electronic properties can be affected by the particular choice of metal. [6][7][8][9] Resulting properties can generally be inferred from the valence and polarization of the host cation along with the required electron donation-hexaborides having di-valent metals tend to produce semiconductors, while inclusion of a tri-valent metal allows for metallic conductivity. Electronic properties near the surface are also affected by the type of metal; however, additional degrees of freedom such as the atomic configuration will also affect observed properties, e.g., catalysis, adsorption, and emission.…”

A generalized method for the inversion of cohesive energy curves from isotropic and anisotropic lattice expansions

“…Setting L O h = 2 Å and calculating the cohesive energy in the range a d = [ 2 + 2 √ 2, 12 + 2 √ 2 ] Å, the inversion process produces inter-octahedral potentials for interatomic separation distances r i j = [ 2,12 ] Å, assuming the conditions given in Eqn (19) are met. Setting L O h = 2 Å and calculating the cohesive energy in the range a d = [ 2 + 2 √ 2, 12 + 2 √ 2 ] Å, the inversion process produces inter-octahedral potentials for interatomic separation distances r i j = [ 2,12 ] Å, assuming the conditions given in Eqn (19) are met.…”

“…In addition, the external modes of vibration are of far smaller frequencies; therefore, the octahedral units effectively act as rigid bodies in comparison to their surroundings. This type of model has recently been used by Schmidt et al 12 to study the energetic and dynamic trends in various metal hexaboride systems. The use of rigid bonds and bodies has the benefit of reducing the number of degrees of freedom of the system, allowing for molecular simulations of greater time and length-scales.…”