UChicago’s Localized Active Space for Materials Research
A revolutionary quantum chemistry method to solve complex materials' mysteries
Localized Active Space
A new computational method for quantum chemistry was developed at the University of Chicago to reconcile physicists' and chemists' historically different perspectives on materials. By using the Localised Active Space (LAS) framework to periodic solids, this innovative method combines local quantum chemistry with global band theory to understand complex materials like organic semiconductors and high-temperature superconductors.
By accurately predicting local electronic activity and electron hopping across parts, the approach can predict how quantum mechanics affects transport characteristics in current materials. The researchers tested the technique on hydrogen chains and p–n junctions and believe it will be vital for developing high-quality materials in the future.
A University of Chicago computational method that combines two long-distance scientific viewpoints may help explain some of the world's most puzzling materials, from solar cell semiconductors to high-temperature superconductors. UChicago researchers may explain how quantum processes in contemporary materials cause transport properties.
Laura Gagliardi, senior author and Richard and Kathy Leventhal Professor in Chemistry at the Pritzker School of Molecular Engineering, says “chemists and physicists have used very different lenses to look at materials for decades.” “We have now developed a methodical approach to integrating those viewpoints,” she said, adding that this gives new tools to understand and build extraordinary materials.
Physicists study materials using huge, recurring band structures, while chemists study electrons in specific molecules or fragments. Metal-organic frameworks, organic semiconductors, and strongly correlated oxides are important materials that don't match either picture. Electrons in these materials jump between repeated fragments instead of being scattered.
Co-first author Daniel King said, “It is possible to accurately describe electrons on individual fragments, but you lose the global picture of how charges move across a material.” The new method squares the circle by modelling local fragments and recording electron hops.
The methodology is based on Research Assistant Professor Matthew Hermes' Localised Active Space (LAS) concept. Using the LAS framework for periodic materials, the researchers combined global band theory with local quantum chemistry.
The researchers tried the method in tough situations to prove its efficacy. Traditional density-function theory methods misclassify hydrogen chains as metals, making them difficult to predict. For more precise approaches, hydrogen chains must be insulators. The innovative Localised Active Space approach accurately showed how hydrogen chain electrons determine the material's insulator characteristics.
Another example was Localised Active Space simulation of a p–n junction, a vital feature of solar cells and computer processors. The technique successfully illustrated the previously difficult process of charges splitting and travelling across the junction when shown light.
Co-first author and fourth-year graduate student in the Gagliardi Group Bhavnesh Jangid called the findings “step one,” saying the technique accurately captures the correct physics. To improve the plan, the team will use various cutting-edge methods.
This method helps scientists understand and create novel materials. King says “at their core, all materials are quantum mechanical.” He noted that this is a significant step towards understanding how quantum mechanics drives everyday phenomena.
The project was partially funded by Q-NEXT, a DOE National Quantum Information Science Research Centre. The Localised Active Space technique is open-source, and the Gagliardi Group aims to improve it so other quantum transport researchers can use it.
