Most fundamental mathematical equations that describe electronic structures are not easy to solve. Progress in physics, chemistry and the material sciences has been hampered by this. Researchers were able to change this situation thanks to the establishment of the simulation method density functional theory. Even though these tools are used, the modeled processes are still simplified. Physicists at the Center for Advanced Systems Understanding and the Institute of Radiation Physics were able to improve the DFT method. In the journal of chemical theory and computation, the group explains that this opens up new possibilities for experiments with ultra-high intensity lasers.
One of the most fundamental challenges of the young investigator group leader is taken on by the lead author and two other authors. Many research fields within physics, chemistry, material science, and related disciplines are based on these quantum many-body systems. Most material properties are determined by the behavior of electrons. The mathematical equations that describe electronic structures are not easy to solve. The understanding of elaborately designed materials is very limited.
Modern high- performance computing clusters have given rise to a new field of computation called quantum many-body theory. Density functional theory has given unprecedented insight into the properties of materials. DFT is an important simulation method in physics, chemistry, and the material sciences. It is able to describe many-electron systems. Over the last decade, the number of scientific publications based on DFT calculations has increased, and companies have used the method to calculate the properties of materials as accurate as ever before.
Coming back from a simplification.
The framework of linear response theory allows for the calculation of many such properties. The concept is used in many experiments in which a laser is used to measure the response of the system to the outside. The system can be diagnosed in this way. Linear response theory makes experiment and theory feasible in the first place. It is still a huge simplification of the processes.
The DFT method is being extended by the researchers in their latest publication. For the first time, experimental results from real materials can be compared to non- linear effects in quantities.
Prior to this publication these effects were only reproduced by a set of Monte Carlo simulations. It requires a lot of computational power to deliver exact results. There is a need for quicker simulation methods.
The DFT approach is 1000 to 10,000 times faster than Monte Carlo calculations. We were able to demonstrate across temperature regimes that this does not affect accuracy. The DFT-based methodology of the non-linear response characteristics of quantum-correlated electrons makes it possible to study new non- linear phenomena in complex materials.
Modern free electron lasers have more possibilities.
The new methodology fits very well to the capabilities of modern experimental facilities like the Helmholtz International Beamline for Extreme Fields, which went into operation only recently. With the help of high power lasers and free electron lasers, we can study these non- linear excitations with unprecedented temporal and spatial resolution. New effects in matter that have not been studied before are ready to be studied.
The Young Investigator Group "Frontiers of Computational Quantum Many-Body Theory" installed in early 2022. We have been involved in the high energy density physics community. We are devoted to pushing the frontiers of science by providing solutions to quantum many-body problems. The advancement in electronic structure theory will be useful for researchers.
More information: Zhandos Moldabekov et al, Density Functional Theory Perspective on the Nonlinear Response of Correlated Electrons across Temperature Regimes, Journal of Chemical Theory and Computation (2022). DOI: 10.1021/acs.jctc.2c00012
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