This exact exchange (EXX) implementation enables Hartree-Fock and hybrid functional calculation (PBE0, HSE) for periodic systems and comes with the following features:

• spin-restricted and unrestricted EXX
• Adaptively Compressed Exchange (ACE)
• restriction to -point sampling of the Brillouine zone
• various techniques to treat the Coulomb singularity at :
  • Probe charge Ewald
  • Wigner-Seitz truncation
  • Spherical truncation
  • Voxel averaging

Check the example file in DFTK.

In his thesis, he systematically evaluated various fragment construction schemes to accurately capture the electronic structure of carbon monoxide adsorbed on titanium dioxide. His highly precise theoretical predictions reveal a significant discrepancy with experimental data, exposing a fascinating puzzle that highlights the complex influence of temperature, vibrations, surface defects and specific measurement techniques on the observed adsorption behavior.

In his thesis, he developed enhanced Davidson algorithms to significantly speed up compression techniques of the virtual orbital space starting from the unbiased plane wave basis. This is particularly useful for correlation workflows (e.g., coupled cluster theory) applied to systems which include a lot of vacuum.

Our paper on noncovalent interactions is now published in Nature Communications. We investigate why two of the most trusted methods in quantum chemistry, CCSD(T) and DMC, have shown puzzling disagreements for large molecules. We identify an issue in the standard CCSD(T) method and show how our CCSD(cT) approach fixes this.

Benjamin Shi has developed a new automated and open-source framework (autoSKZCAM) for molecular adsorption on ionic materials by leveraging a multilevel embedding approach. This makes it practical to apply highly accurate correlated wavefunction theory, achieving results comparable to experiments at a manageable computational cost. It was an honor to contribute to this work in a great collaboration with Benjamin X. Shi, Andrea Zen, Angelos Michaelides, and coworkers.

This work demonstrates that one of the most widely-used and accurate quantum chemistry approaches – CCSD(T) theory – in certain cases binds noncovalently interacting large molecular complexes too strongly. Our findings show that a simple yet efficient modification denoted as CCSD(cT) remedies these shortcomings.

In this publication we introduce a novel finite-size correction scheme to enable coupled cluster theory for highly accurate materials modeling of metals. Using the example of metal surface energies, which are highly relevant due to their wide range of applications, we demonstrated that this observable can be reliably reproduced with high precision for the first time.

In his thesis Orbital Localization in Solids by Riemannian Optimization he implemented and tested different optimization algorithms like BFGS, CG, and SA for orbital localization. Specifically he focused on Intrinsic Bond Orbitals (IBOs). The unitary constraints involved in orbital transformations are inherently satisfied through Riemannian optimization, where cost functions are optimized on Riemannian manifolds.

In this work he focused on two questions: (1) Does the suitability to construct sparse tensors of localised orbitals deteriorate for materials with small band gaps and diffuse density? (2) Are there trends in the orbital spreads or the sparsity concerning the bandgap or lattice constant? We will be publishing the intriguing results soon.