First-principles modeling of the H color centers in MgF2 crystals

MgF₂ with a rutile structure is important wide-gap optical material with numerous applications. We present and discuss the results of calculations for basic hole defects - interstitial F atoms (called also the colour H centers). This study is based on the large scale ab initio DFT calculations using hybrid B3PW exchange-correlation functional as implemented into CRYSTAL computer code. The electronic structure, atomic geometry, charge density distribution are calculated and compared with similar defects in CaF₂ fluorite. It is shown that the H centers oriented nearly parallel to the (110) axis are energetically more favourable than those oriented along the (001) axis, in agreement with experiment.