The innovation engine for new materials

Meredith Goudreau

Meredith Goudreau




Las Positas College


Emily Morgan

Faculty Sponsor(s): 

Ram Seshadri

Faculty Sponsor's Department(s): 

Materials Research Laboratory

Project Title: 

Solid-State Synthesis and Density Functional Theory Investigation of Mo-Based Vacancy Ordered Double Perovskites

Project Description: 

Vacancy-ordered double perovskites, with general formula A2BX6, are a variant of the standard  perovskite structure derived by doubling the unit cell in three dimensions and removing alternate  B-site cations. Due to their isolated octahedra, these perovskites exhibit a marked decrease in  polyhedral connectivity, which allows for ready synthetic substitution upon all three lattice sites. Thus, these compounds are excellent model systems for evaluating trends in the magnetic and  optoelectronic properties of less readily tunable classes of perovskites, such as CH3NH3PbI3, that  are currently utilized in a wide variety of photovoltaic applications. Prior analysis of the Ru based compounds (A2RuX6) has shown that their functional behavior is dependent upon the  identity of both the X-site halide anion and the A-site cation. Therefore, this research devises a  practical method for synthesizing Mo-based vacancy-ordered double perovskites (A2MoX6) in  order to determine whether they exhibit comparable chemical tunability. We explored a variety  of solid-state synthesis routes and characterized the resultant products using x-ray diffraction. Additionally, density functional theory (DFT) computations were used to rationalize the  experimental results by predicting the expected magnetic and electronic behavior of these  compounds. We systematically investigated the effect that various substitutions on different  lattice sites had on the properties of the Mo-based perovskites. Preliminary DFT computations  have indicated that spin orbit coupling (SOC) significantly impacts the electronic properties of  these perovskites. Based on these first principles calculations, we anticipate that the Mo-based  vacancy-ordered double perovskites will behave similarly to the Ru-based compounds with  ready chemical tunability on both the A-site cation and X-site halide anion. We intend to further  extend our research by examining the W-based versions of these compounds, which exhibit  much stronger SOC effects. These findings serve as an integral step towards establishing a  simple set of rules to describe the electronic and magnetic properties of the family of vacancy ordered double perovskites.