Open AccessOptical properties of (Mg0.97, Fe0.03)O ferropericlase under the pressure of the Earth’s lower mantle
Author(s) -
Min Gao,
Shu Wen-Lu,
Qiang Ye,
He Lin,
Weiliang Zhu
Publication year - 2015
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.64.119101
Subject(s) - materials science , spin transition , absorption spectroscopy , refractive index , crystal (programming language) , absorption (acoustics) , spin crossover , infrared , mantle (geology) , condensed matter physics , chemical physics , optics , optoelectronics , chemistry , composite material , geology , physics , geophysics , computer science , programming language
The optical-absorption and refractive-index properties of (Mg0.97, Fe0.03)O ferropericlase crystals without and with Mg and O ionic divacancy point-defect under the pressure of the Earth’s lower mantle are investigated using the first-principles calculations. Optical-absorption data show that the perfect-crystal results are similar to the predictions from the crystal-field theory:the pressure-induced spin transition of iron in ferropericlase causes a large blue-shift in its optical-absorption spectrum, leaving the near-infrared region transparent. However, when there are point defects in ferropericlase, the calculated optical-absorption results are completely inconsistent with predictions from the crystal-field theory, the spin transition causes the enhancement in the optical absorption in the near-infrared region. Refractive-index data of defect crystal indicate that the effects of pressure, wavenumber, and spin-transition on the high-pressure refractive-index of (Mg0.97, Fe0.03)O ferropericlase are obvious, but perfect-crystal results show that those effects should be relatively weak. The 15%-20% iron-bearing ferropericlase is currently considered as an important mineral in the Earth’s lower mantle. Due to similar characteristics of the observed high-pressure optical-absorption spectrum in ferropericlase with different iron content, we suggest that:(1) the above-mentioned calculated results is conducive to the understanding of high-pressure optical properties of lower-mantle ferropericlase and the exploring of the origin of discrepancies in its high-pressure optical-absorption spectrum between experiment and crystal-field theory; (2) the high-pressure optical-absorption spectrum measurements may be a good approach for probing iron spin state.