Phase Stability and Thermoelectric Properties of the Mineral FeS₂: An Ab Initio Study

Abstract

First principles calculations were carried out to study the phase stability and thermoelectric properties of the naturally occurring marcasite phase of FeS 2 at ambient condition as well as under pressure. Two distinct density functional approaches has been used to investigate the above mentioned properties. The plane wave pseudopotential approach was used to study the phase stability and structural, elastic, and vibrational properties. The full potential linear augment plane wave method has been used to study the electronic structure and thermoelectric properties. From the total energy calculations, it is clearly seen that marcasite FeS 2 is stable at ambient conditions, and it undergoes a first order phase transition to pyrite FeS 2 at around 3.7 GPa with a volume collapse of about 3%. The calculated ground state properties such as lattice parameters, bond lengths and bulk modulus of marcasite FeS 2 agree quite well with the experiment. Apart from the above studies, phonon dispersion curves unambiguously indicate that marcasite phase is stable under ambient conditions. Further, we do not observe any phonon softening across the marcasite to pyrite transition and the possible reason driving the transition is also analyzed in the present study, which has not been attempted earlier. In addition, we have also calculated the electronic structure and thermoelectric properties of the both marcasite and pyrite FeS 2 . We find a high thermopower for both the phases, especially with p-type doping, which enables us to predict that FeS 2 might find promising applications as good thermoelectric materials.

Outstanding thermoelectric performances for both p- and n-type SnSe from first-principles study

“…This approximation assumed that the scattering time determining the electrical conductivity would not vary strongly with energy on the scale of kT. This method has been widely used to calculate transport properties of thermoelectric materials [11][12][13][14][15][16][17][18][19][20][21].…”

Enhanced thermoelectric performance of layered SnS crystals: the synergetic effect of temperature and carrier concentration

“…In this package, the grid of T is dened by T max in the input le. [38][39][40][41] 3. In RBA, it is assumed that the band structure of the host is unchanged by doping.…”

Periodic DFT+U investigation of the bulk and surface properties of marcasite (FeS2)

“…In earlier studies, the phase stability and thermoelectric properties of the naturally occurring marcasite phase of FeS2 under ambient conditions has been investigated using firstprinciples calculations. 18,25 Total energy calculations show that marcasite FeS2 was stable at ambient conditions, and that it undergoes a first-order phase transition to pyrite FeS2 at around 3.7−5.4 GPa at 0 K. 18, 25 Reich and Becker have also employed first-principles and Monte Carlo calculations to investigate the thermodynamic mixing properties of arsenic into bulk pyrite and marcasite. 26 From their calculated enthalpies, configurational entropies and Gibbs free energies of mixing, it was shown that the two-phase mixtures of FeS2 (pyrite or marcasite) and FeAsS (arsenopyrite) are energetically more favorable than the solid solution Fe(S,As)2 (arsenian pyrite or marcasite) for a wide range of geologically relevant temperatures.…”