FIRST PRINCIPLES MOLECULAR MODELING OF THE JAROSITE MINERAL GROUP: THERMODYNAMIC CALCULATIONS USING VARIABLE SPACE GROUP DESIGNATIONS TO DETERMINE THE SYMMETRY RELATION TO STABILITY FROM AB INITIO QUANTUM MECHANICAL DENSITY FUNCTIONAL THEORY TECHNIQUES

The jarosite mineral group has come to the forefront of planetary geology since it was discovered on the surface of Mars by the Mars Exploration Rover - Opportunity in 2004. Analytical techniques have reported considerable variations in the space group designations of this mineral group. These variations are likely due to entropy differences in the formation environment that result in alternative crystal symmetries. A fundamental investigation of this phenomenon has yet to be undertaken. This study is a preliminary determination of the ability of density functional theory generalized gradient approximations (DFT-GGA) to accurately determine general thermodynamic parameters of the jarosite mineral group. Calculations using variations in space group designation were performed to better understand the effect that space group and symmetry have on density functional theory approximations of thermodynamic variables in the complex crystal structure of jarosite. Theoretical values were compared to experimental values to determine the validity of the DFT-GGA technique and to determine the role that symmetry has on the stability of the mineral group. In order to accomplish calculations of this magnitude, we have employed the Columbia supercomputer at NASA Ames advanced computing center which has allowed us to complete calculations using all the current variations of DFT-GGA. These results are a gateway to determining the validity of using theoretical methods for large complex mineralogical systems. Application of theoretical techniques based on first principles approximations will allow mineralogists to accurately predict the properties of minerals from theoretical thermodynamic calculations and apply them to extraterrestrial environments.