Tobias Schäfer

Our paper on noncovalent interactions is now published in @natcomms.nature.com. doi.org/10.1038/s414...
We investigate why two trusted quantum chemistry methods have shown discrepancies for large molecules. We identify and correct over-strong bonds through the CCSD(T) method. #compchem

05.11.2025 07:39 — 👍 8    🔁 1    💬 0    📌 0

Convergence and Properties of Intrinsic Bond Orbitals in Solids We present a study of the construction and spatial properties of localized Wannier orbitals in large supercells of insulating solids using plane waves as the underlying basis. The Pipek-Mezey (PM) functional in combination with intrinsic atomic orbitals (IAOs) as projectors is employed, resulting in so-called intrinsic bond orbitals (IBOs). Independent of the bonding type and band gap, a correlation between orbital spreads and geometric properties is observed. As a result, comparable sparsity patterns of the Hartree–Fock exchange matrix are found across all considered bulk 3D materials, exhibiting covalent bonds, polar covalent bonds, and ionic bonds. Recognizing the considerable computational effort required to construct localized Wannier orbitals for large periodic simulation cells, we address the performance and scaling of different solvers for the localization problem. This includes the Broyden–Fletcher–Goldfarb–Shanno (BFGS), Conjugate-Gradient (CG), Steepest Ascent (SA), as well as the Direct Inver-sion in the Iterative Subspace (DIIS) method. Each algorithm performs a Riemannian optimization under a unitary matrix constraint, efficiently reaching the optimum in the “curved parameter space” on geodesics. The solvers have been implemented both within the VASP and as a standalone open-source software package. Furthermore, we observe that the construction of Wannier orbitals for supercells of metal oxides presents a significant challenge, requiring approximately 1 order of magnitude more iteration steps than other systems studied.

We benchmark different Riemannian solvers for orbital localization (Intrinsic Bond Orbitals) in large-scale solids. We find the Fock exchange matrix sparsity is robust and independent of the band gap for several 3D insulators.
@pubs.acs.org #compchem
pubs.acs.org/doi/10.1021/...

05.11.2025 07:35 — 👍 2    🔁 0    💬 0    📌 0

Metal surface energies can now be reliably predicted using coupled cluster theory, enabled by a novel finite-size correction scheme. A significant advancement in accurate materials modeling. #compchem
pubs.acs.org/doi/10.1021/...

18.12.2024 17:48 — 👍 21    🔁 2    💬 0    📌 1