What happens when you remove certain symmetries in the crystal structure of quantum materials? In particular, when one removes inversion symmetry. Our group synthesizes transition metal chalcogenides with layered-type structures in order to 'twist' or 'bend' them to make them non-centrosymmetric and induce new physical phenomena. Such a strategy could, for example, lead to novel pairing mechanisms in superconductors. To do this bending or twisting, we insert metal amine species between the chalcogenide layers, taking advantage of the van der Waals gap and hydrogen bonding of the type N--H-Q where Q= chalcogenide anion such as S^2- or Se^2-. The metal amine species is a chiral molecule itself such as M(en)₃ where M = coordinating metal and en=ethylenediamine. With advanced scattering measurements that include synchrotron X-rays and neutrons, we study the key structure-property relationships of our materials. The layered host is typically a tetrahedral transition metal chalcogenide (TTMC) where MQ₄ tetrahedra edge-share to make 2D layers. Below, a schematic our non-centrosymmetric quantum materials, which include chalcogenides of iron, cobalt, manganese and nickel.

Ferroics such as ferromagnets, ferroelectrics, and ferroelastics are crystalline materials whose characteristic properties are dictated by and understood through their symmetry. A defining characteristic of these materials are that the magnetic moments, electric dipoles, etc. will spontaneously align at a specific transition temperature. This ordering is used to both understand the orientation of their spontaneous physical properties, and properties under applied fields. Through the lens of solid-state chemistry, we are searching for a new class of ferroic materials called ferrotoroidics. We define a toroidal moment as the local moment that arises from a local vortex of magnetic moments. When considering materials to target for synthesis, we consider both the point group symmetry which would permit novel ordering, and structural components which enable this ordering. We began by studying the series of lithium transition metal orthophosphates LiMPO4 (M = Mn, Fe, Co, Ni), whose magnetic point group symmetry is known to permit ferrotoroidic order in the iron, cobalt, and nickel analogs. We have begun also investigating other systems also containing magnetic transition metal cations and tetrahedral anions, such as thiophosphates, silicates, and pyroxenes. The figure below depicts two candidate structures for ferrotoroidics. To study the subtle features of the magnetic ordering in our materials, we are currently building the polarized neutron apparatus and infrastructure to perform spherical neutron polarimetry on these and other materials.

Chemical warfare agents (CWA) prevalently threaten military and civilian populations. To ensure their protection, new materials need to be developed that can adsorb and degrade these CWAs. Current filters use an activated carbon to adsorb the CWA and ASZM-TEDA to degrade them. To increase reactivity, we synthesize mesoporous metal oxides (MMO) using a variety of techniques including hard and soft templating to increase the surface area and overall reactivity. We study how CWAs and probe molecules such as degrade on the surfaces in the pores of the MMOs through various spectroscopic techniques. We start with simple binary oxides such as TiO₂ and CeO and then characterize how aliovalent doping promotes or degrades reactivity towards CWAs or DMMP. We are look at complex oxides such as those with the perovskite structure; examples include ATiO₃ (A = Ca, Sr, Ba) and LaBO₃ (B = Mn, Fe, Co, Ni). We explore how different porous structures (e.g. KIT-6, SBA-15, CMK-3, FDU-15 ect.) affect structure effect reactivity. This project is highly collaborative, working with other research groups for computational (e.g. DFT) studies of surface reactivity and specroscopic studies (e.g. infrared, mass spectrometry) to understand thermodynamics and kinetics. Prof. Maija Kukla (UMD) peforms DFT calculations and Prof. Michael Zachariah (UC Riverside) conducts the kinetic and thermodynamic studies. Finally, the Chemical Biological Center (CBC, DEVCOM) tests our materials with live agents.

Oxygen storage materials are substoichiometric metal oxides which can be used for a variety of applications including fuel cells, energy conversion, combustion, chemical looping cycles, and catalysis. We explore through the use of in-situ synchrotron X-ray and neutron scattering how metal oxides evolve in structure and chemical composition as the uptake and release oxygen. Some of the systems we explore include 'traditional' perovskites such as La_1-xSr_xBO₃ where B = Mn, Fe, Co, and Ni. Less explored by the community are the layered oxides with stoichiometry AB₂O₄ where A = Ln³⁺ and B= Mn, Fe, and Co. In the case of perovskites, usually one is creating and oxide vacancies and the oxygen storage capacity is given by δ in ABO_3-δ. In the case of the layered oxides, oxide anions are incorporated into crystalline lattice. Therefore, the oxygen storage capacity is given by δ in AB₂O_4-δ.