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MAX-phases and MXenes

A prominent example of interesting nanolaminates are the so-called MAX-phases, which are either hexagonal ternary carbides or nitrides. The MAX-phases are known to exhibit a remarkable combination of chemical, physical and mechanical properties including e.g., high electrical and thermal conductivity, high strength, high dissociation temperature, corrosion resistance, low friction, resistance to thermal shock and easy machinability. Another objective is to investigate the anisotropy characteristics in the electronic structure of so-called MXenes, a new family of 2D ceramic crystals related to MAX-phases.

Amorphous carbides

The objective of this work is to investigate the electronic structure in amorphous nanocomposite carbides and metallic glasses. A differentiation between the largely unknown electronic occupation of orbitals and bond strengths in octahedral and prismatic coordination in the interior of amorphous nanocomposites in comparison to single crystal materials using bulk-sensitive and element-selective x-ray spectroscopies are made. The knowledge aims to facilitate synthesis of novel amorphous materials and metallic glasses for hard coatings and electrical contacts on the atomic scale, and also serve as important tests of stochastic quenching density functional theory (SQ-DFT) and molecular dynamics (MD) simulations, enabling development of improved theoretical methods.

Wide band-gap nitrides and strongly correlated materials

This research aims to explore the development of the width of the band-gap and anisotropy in the electronic structure of wide band-gap nitrides by investigating the hybridization and orbital overlap of the containing elements. The investigations have impact on future studies on other complex doped, ordered, and alloyed systems, e.g., temperature-dependent low-energy excitations and charge-transfer mechanisms and related inherently nano-laminated materials with temperature-dependent orbital occupations. Another objective is to explore low-energy excitations and charge-transfer processes in strongly correlated systems such as H-Tc superconductors and Colossal Magnetoresistance materials. The temperature-induced metal-insulator phase transitions and changes in the electronic structures at phase transitions are studied. The studies have impact on the fundamental understanding of electron correlations in relation to crystallographic direction-dependent physical properties such as conductivity.

Research Tools

Experimental techniques

X-ray spectroscopy: soft x-ray absorption spectroscopy (XAS or SXA), X-ray Raman scattering or Soft x-ray emission spectroscopy (XES or SXE), Resonant inelastic x-ray scattering (RIXS), Extended X-ray Fine Structure Spectroscopy (EXAFS), X-ray Magnetic Circular Dichroism (XMCD). Most of the spectroscopic research is based on measurements at synchrotron radiation facilities.

Calculational methods

Density functional theory (Wien2k, Exciting, FEFF, CASTEP in Materials Modelling), Crystal-field, ligand-field and charge-transfer multiplet calculations in SIAM.

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