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In this paper, we used the first principles (CASTEP) method to calculate the electronic properties ferropericlase (Mg0.9375Fe0.0625O) under 0 and 80 GPA. The calculated band gaps show that ferropericlase is a metal under 0 GPA, while it is a narrow-band semiconductor at 80 GPA. The ferropericlase at 0 GPA has some magnetic moment, while it has no moment at 80 GPA. The relations between band and Mg 2p, 2s Fe 3d and O 2s, 2p versus DOS have been discussed. We also find the ferropericlase exhibits metal behavior at some energies. Our calculations not only provide a reference to identify the ferropericlase in geological specimen but stimulate experiments in future. Introduction Ferropericlase is an important mineral in the mantle [1-4]. Ferropericlase is under high pressure in the mantle [5, 6]. The electronic properties of ferropericlase should be studied to identify the behavior of ferropericlase in the mantle. The properties can also be used to identify ferropericlase in geological specimen. Based on the reasons, more and more experts devote to studying ferropericlase under pressure [7-9]. Some experts used the high-pressure equipments [10, 11], which have high running costs. On the other hand, stimulations by computer provide a cheap and fast method to study the properties of ferropericlase. Among these stimulate method, the first principles method is an effective method to study the properties of materials under pressure [12-14]. In this paper, we intend to study the electronic properties of ferropericlase under pressure. Computational details Our calculations have been performed in a program (CASTEP) in Materials Studio software [15]. We first built an Mg0.9375Fe0.0625O supercell (Fig. 1). The obtained iron content is 6.25%, which is a typical value of ferropericlase. The used pressures are 0 and 80 GPa, which is a typical pressure in the mantle. After test, we used 400 eV as the cutoff energy. The k points for first Brillouin zone used in our calculations is 3×3×6. The valence electrons used in our calculations are 2p3s, 2d4s and 2s2p for Mg, Fe and O, respectively. Ultrasoft pseudopotential was used in our calculations. Our calculations were performed in a reciprocal space. The tolerance of the SCF is 5e eV/atom. We first optimized the structure and then calculated the electronic properties. Results and discussions Structure and bands. The optimized lattice constants of Mg0.9375Fe0.0625O under 0 GPA is a=b=4.31 and c=4.27 Å, while the constants under 80 GPA is a=b=3.88 and c=3.88 Å. We can see that the pressure decreases the lattice constants. The decreased ratios of a (b) and c are 10.0% and 9.1%. The constants in MgO are equal to each other. After Fe doping, the constant is not equal. The rate of the decreasing is not equal to each other. Pressure induces the constants equal to each other. The lattice constants a, b and c are not equal under 0 GPa, while these constants equal to each other under 80 GPa. International Conference on Information Sciences, Machinery, Materials and Energy (ICISMME 2015) © 2015. The authors Published by Atlantis Press 730 Cell angles (α, β and γ) are all 90°. The pressure can change the lattice constants but cannot change the cell angels. Fig. 1. The scheme crystal of Mg0.9375Fe0.0625O. Fig. 2. Bands of Mg0.975Fe0.625O under 0 GPa (left) and 80 GPa (right). Density of states. Fig. 3. The density of states (DOS) of Mg0.975Fe0.625O under 0 GPA (left) and 80 GPA (right).The density of states (DOS) relate closely to study the band. In this section, we calculated the DOS and discuss the relation between DOS and band. The calculated DOS shows of Fig. 3. The left of Fig. 3 (Mg0.975Fe0.625O under 0 GPa) shows there is a net magnetic moment around the Fermi level, which means Mg0.975Fe0.625O under 0 GPa is a magnetic material. The DOS above

The electronic properties of ferropericlase under pressure calculated by first principles