This proposal aims to advance the understanding of the fundamental parameters governing the electronic properties of two-dimensional (2D) materials, with a particular focus on band structures, core-level chemical shifts, and Fermi surface topologies. These properties are critical for interpreting and optimizing the electronic transport characteristics of 2D systems. A central material class under investigation is the family of transition metal carbides and nitrides known as MXenes. These semiconducting Mn+1Xn-layered compounds (where M is a transition metal and X denotes carbon and/or nitrogen) exhibit significant potential across a wide range of technological applications, including lithium-ion batteries, supercapacitors, fuel cells, solar cells, water-splitting catalysts, and 2D nanoelectronic devices such as field-effect transistors. In addition to ongoing work on MXenes, the project will continue to perform density functional theory (DFT) calculations to complement and interpret experimental spectroscopic data—specifically valence band X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and resonant inelastic X-ray scattering (RIXS). These calculations are directly connected to ongoing research led by Ph.D. student Susmita Chowdhury (project start: 2023-01-01), with a focus on 2D scandium nitrides exhibiting enhanced thermoelectric properties. Theoretical insights will be essential for accurate interpretation of data obtained from beamline experiments at the MAX IV Laboratory. The proposal also encompasses DFT-based studies of the electronic structure, chemical bonding, and chemical shifts in recently discovered monolayers and trilayers of Goldene, a 2D phase of gold, as well as thermoelectrically active nitride systems. These studies are extended to mono-, bi-, and trilayer systems and compared with corresponding bulk materials, to explore dimensionality effects. Additionally, calculations will investigate related novel 2D metals—tentatively referred to as "metallenes"—including Silverene, Iridiumene, and Platinumene. Computational efforts will involve structural relaxations and self-consistent field (SCF) calculations using state-of-the-art DFT codes such as VASP, WIEN2k, and OCEAN. Theoretical results will be systematically compared with experimental data from XAS, XANES, EXAFS, XPS, ARPES, and RIXS collected at the MAX IV synchrotron facility in Lund. For 2025, we have been awarded competitive beamtime allocations at MAX IV for measurements including XAS, XPS, X-ray emission spectroscopy (XES)/RIXS, and ARPES on a range of 2D materials. To fully exploit this opportunity, it is essential to produce accurate DFT-based simulations that can be directly compared with experimental observations. Moreover, Ph.D. student Susmita Chowdhury continues to produce experimental data from MAX IV, which requires consistent theoretical support through the same computational framework. Presently, we are working on several publications and need more time to finish the calculations, esperically to achieve improved agreement with experiment. Previous results on MXene were published in the papers: 1. Fermiology and band structure of oxygen-terminated Ti3C2Tx MXene; Martin Magnuson, Per Eklund, and Craig Polley; Phys. Rev. Lett. 134 106201 (2025). DOI: https://doi.org/10.1103/PhysRevLett.134.106201 2. Interaction and kinetics of H2, CO2, and H2O on Ti3C2Tx MXene probed by X-ray photoelectron spectroscopy; Lars-Åke Näslund, Esko Kokkonen, Martin Magnuson; Appl. Surf. Sci. 684 161926 (2025). DOI: https://doi.org/10.1016/j.apsusc.2024.161926 3. The Origin of Ti 1s XANES Main Edge Shifts and EXAFS Oscillations in the Energy Storage Materials Ti2CTx and Ti3C2Tx MXenes; Lars-Åke Näslund and Martin Magnuson; 2D Mater. 10, 035024, (2023). DOI: https://doi.org/10.1088/2053-1583/acd7fe 3. Chemical Bonding of Termination Species in 2D Carbides Investigated through Valence Band UPS/XPS of Ti3C2Tx MXene; Lars-Åke Näslund, Mikko Mikkela, Esko Kokkonen, and Martin Magnuson; 2D Materials 8, 045026 (2021). DOI: https://doi.org/10.1088/ 2053-1583/ac1ea9 5. Local chemical bonding and structural properties in Ti3AlC2 MAX phase and Ti3C2Tx MXene probed by Ti 1s X-ray absorption spectroscopy; Martin Magnuson and Lars-Åke Näslund; Phys. Rev. Research 2, 033516 (2020). DOI: https://doi.org/10.1103/PhysRev Research.2.033516 6. Chemical Bonding in Carbide MXene Nanosheets; Martin Magnuson, Joseph Halim and Lars-Åke Näslund; J. Elec. Spec. 224, 27-32 (2018). DOI: https://doi.org/10.1016/j.elspec.2017. 09.006. Links: https://www.maxiv.lu.se/article/unveiling-the-properties-of-a-versatile-2d-material-for-energy-storage-and-production-applications-2/ https://www.maxiv.lu.se/article/first-users-at-balder-beamline-seek-to-illuminate-mxenes/ https://www.maxiv.lu.se/article/local-bonding-environment-in-2d-transition-metal-carbides-investigated-by-balder-users/ https://liu.se/en/news-item/enormt-mikroskop-hjalper-liu-forskare-skraddarsy-nya-material/