Disorder in Materials
By modeling materials as they are used experimentally including disorder, we seek to improve fundamental understanding of how the chemical physics of a material leads to measured properties.
Check out our recent Persepective on modeling defects in inorganic materials: Lessons learned from catalysis to qubits: General strategies to build accessible and accurate first-principles models of point defects
Disorder in Inorganic Materials
Crystalline inorganic materials have been the backbone of electronic devices for decades. Computational projects can accelerate the progress of materials research: reducing the costs required for each discovery and increasing understanding of the effect of dopants or defects. While bulk structures are being rapidly reported, materials for solar energy generation and storage are often doped or used in nanostructures to decrease fabrication cost, increase performance, or provide a desired property. In particular, dopants are often required to increase the charge carriers in materials, defects often are a by-product of fabrication and may either help or hinder charge movement in the material, and which surface is exposed in devices can have a large impact on the chemistry and physics that can occur in the device.7 Understanding how dopants, defects, and other forms of disorder in crystalline materials affect the properties of these materials is critical to designing better materials. We use a verity of planewave and localized basis set implementations of density functional theory to study the reactivity, stability, and energetics of disordered inorganic materials.
Relevant References
A-site doping to alter oxygen vacancy diffusion in SrTiO3. ACS Omega, 2024, DOI: 10.1021/acsomega.4c04099
Predicting Electronic Structure of Realistic Amorphous Surfaces. Adv. Theory Simul., 2023, DOI: 10.1002/adts.202300292
Preparing experimentally representative faceted titantia nanoparticle models that are computationally tractable. Int. J. Quant. Chem., 2022 DOI: 10.1002/qua.27062
Mn environment in doped SrTiO3 revealed by first-principles calculation of hyperfine splittings. Appl. Phys. Lett., 2022 DOI: 10.1063/5.0096788
Parameter Space Exploration Reveals Interesting Mn-doped SrTiO3 Structures. PhysChemChemPhys, 2021 DOI: 10.1039/D1CP02417E with cover DOI: 10.1039/D1CP90215F
Disorder in organic Materials
In addition, organic materials have the advantage of being flexible, cheap, and tunable for applications like light-emitting diodes (LEDs), thin-film transistors (TFTs), and photovoltaic cells. Modeling completely ordered periodic structures with accurate electronic structure methods provides detailed band structure and orbital overlap information which can be used to predict transport properties. However, a frozen, perfectly periodic structure might not be a good approximation of a working device, e.g. thin-film-transistors or bulk heterojunction solar cells, where these materials are consistently less ordered. In addition, one would expect different transport properties for different packing densities, polymorphs, and composite structures, which are of great technological interest.
While assuming that the nuclear motions are small on the time scale of the electronic motions is a good approximation in single molecules or very ordered inorganic crystals, in systems where transport is modulated by orbital overlap, like in organic crystals, small molecular vibrations can dramatically change the amount of interaction between molecules. Calculating how the electronic structure changes when including vibration allow us to explore if the large differences in mobility in very similar materials might arise from phonon assisted transport where the inherent molecular vibrations bring a low energy transport path into resonance.
Relevant References
Efficiently Predicting Anisotropic Charge Carrier Mobilities in Organic Materials with the Boltzmann Transport Equation. J. Chem. Phys., 2023, DOI: 10.1063/5.0128125
Real Temperature Model of Dynamic Disorder in Molecular Crystals. J. Phys. Chem. A, 2022 DOI: 10.1021/acs.jpca.2c02120 with cover DOI: jpcafh/126/20
Investigation of transient localization in organic transistors: correlating anisotropic mobility and normal modes. Comm. Physics, 2019 DOI: 10.1038/s42005-019-0129-5
Experimental:
Substantial Recoverable Energy Storage in Percolative Metallic Aluminum-Polypropylene Nanocomposites. Adv. Funct. Mater. 2013 DOI: 10.1002/adfm.201202469
Sustainable High Capacitance at High Frequencies: Metallic Aluminum-Polypropylene Nanocomposites. ACS Nano 2012 DOI: 10.1021/nn3044148
Enhanced Energy Storage and Suppressed Dielectric Loss in Oxide Core-Shell Polyolefin Nanocomposites by Moderating Internal Surface Area and Increasing Shell Thickness. Adv. Mater. 2012 DOI: 10.1002/adma.201202183
In Situ Catalytic Encapsulation of Core-Shell Nanoparticles having Variable Shell Thickness. Dielectric and Energy Storage Properties of High-Permittivity Metal Oxide Nanocomposites, Chem. Mater. 2010 DOI: 10.1021/cm1009491