Bulk FeS2 Properties

GGA property calculation on optimized bulk pyrite has been performed. The calculated band structure and frontier orbital distribution are presented in Fig. 9.3 and Fig. 9.4. The calculated band gap of FeS2 is 0.97 eV, and it is in good line 

In bulk FeSa, each Fe atom is coordinated with six S atoms and each S atom is coordinated with three Fe atoms and one S atom. Fe atom has two free electrons and S has 6 free electrons. For S atom, one electron is used to form S— S dimmer and the other 5 electrons are used to form Fe— S bond. For Fe atom, all the free electrons are shared by Fe— S bond. That is to say the electron contribution of Fe atom to each Fe— S bond is 2/6 and that of S atom is 10/6. When the crystal is cleaved from (100) directions, only Fe—S bonds is broken (see Fig. 9.6). Then the 6-fold Fe atom becomes 5-fold Fe atom and 4-fold S atom becomes 3-fold S atom. Thus, it will produce dangling bonds and surface states. 

---

Abstract In the light of quantum chemistry, sulphide minerals and the interaction of them with reagents are investigated in this chapter. With the density functional theory pyrite is first researched including its bulk properties about energy band and frontier orbitals and the property of FeS2 (100) surface. 

A lot of work (Opahle et al, 2000 Andrew et al, 2002a,b Muscat et al, 2002 Edelbro et al, 2003) has been performed on bulk and surface properties of FeS2 using various kinds of density functional theory. These works have shown that such methods are capable of producing calculated bulk properties such as lattice constants which agree well with experiment, and has provided a reference for the study of pyrite surfaces. 

---