First-principles calculations for the H center in SrF2 crystals

Area of Science:

• Solid State Physics
• Materials Science
• Computational Chemistry

Background:

• H-center defects in fluorite (CaF2, SrF2, BaF2) crystals are crucial for understanding their optical and electronic properties.
• Previous studies have explored various defect configurations, but a comprehensive analysis of H-center stability and electronic structure in SrF2 is needed.

Purpose of the Study:

• To simulate and determine the most stable ground state configuration of H-center systems in SrF2 crystals.
• To investigate the geometric, energetic, and electronic structure of H-center defects with different orientations.
• To clarify the constituents of defect bands and the location of the hole in the H-center system.

Main Methods:

• Hybrid Hartree-Fock and density functional theory (DFT) calculations using Becke's three-parameter hybrid method (B3PW91).
• Simulation of H-center systems in SrF2 oriented along [100] and [111] crystallographic axes.
• Analysis of geometric relaxations, formation energies, electronic structure, effective charges, spins, band structures, and density of states.

Main Results:

• The H-center oriented along the [111] axis is found to be the most stable configuration in SrF2.
• Geometric relaxations of neighboring atoms around the H-center were calculated for both orientations.
• The hole in the [111]-oriented H-center system is localized at the interstitial fluorine atom, as indicated by effective charge and spin analysis.

Conclusions:

• The [111] orientation represents the most energetically favorable configuration for H-center defects in SrF2.
• The electronic structure calculations reveal the localization of the hole, providing insights into defect behavior.
• Understanding these defect properties is essential for potential applications of SrF2 in optical and electronic devices.