Rescent research topics

• Mean-Field Density Matrix Decompositions
  Lossless property decompositions of HF & KS-DFT into either bond-wise or atomic contributions.
  
  I've introduced a new and robust decompositions of mean-field Hartree-Fock (HF) and Kohn-Sham density functional theory (KS-DFT) relying on the use of localized molecular orbitals and physically sound charge population protocols, cf. ref 1. The new lossless property decompositions, which allow for partitioning 1-electron reduced density matrices into either bond-wise or atomic contributions, are intended to be employed in possible applications as an interpretative tool in the rationalization of certain electronic phenomena as well as for exposing and amplifying compositional features in the context of machine-learned quantum chemistry. Recent applications of the theory include ref. 2.
  
  The DECODENSE code is open source: https://github.com/januseriksen/decodense
  
  
  
  
  Comparison of bond- and atom-partitioned contributions (in units of Hartree) to the total KS-DFT (TPSSh xc functional) energy of the benzene molecule (Fig. from doi/10.1063/5.0030764).

• Contemporary Near-Exact Quantum Chemistry
  Assessments of modern near-exact electronic structure theory.
  
  Leading a broad, international consortium of research groups, I've worked on the blind assessment of a wide range of contemporary near-exact electronic structure methods. Specifically, we've reported (in ref. 3) on the findings of a blind challenge devoted to determining the frozen-core, full configuration interaction (FCI) ground-state energy of the benzene molecule in a standard correlation-consistent basis set of double-ζ quality. Subsequently, I've been invited to comment on the status of current state-of-the-art approaches in a perspective on the field (ref. 4), nearly a century on from the dawn of modern quantum mechanics.
  
  

Other research topics

• Many-Body Expanded Full Configuration Interaction
  Near-exact properties for both weakly and strongly correlated molecular systems in extended basis sets.
  
  
• HPC- and GPU-Accelerated Quantum Chemistry
  Efficient implementation of coupled cluster methods on parallel CPU and GPU hardware.
  
  
• Coupled Cluster Perturbation Theory
  Theoretical development of Lagrangian-based many-body perturbation theory.
  
  
• Local Coupled Cluster Methods
  Implementation and application of the DEC-CCSD(T) computational method.
  
  
• Polarizable Embedding Theory
  Polarizable solvent modelling by means of either DFT or many-body methods.