Computational and Quantum Chemistry

💧 𝗙𝗨𝗡 𝗙𝗔𝗖𝗧 𝗢𝗙 𝗧𝗛𝗘 𝗗𝗔𝗬 — Molecular Simulation A seemingly tiny 10 × 10 × 10 nm³ box of liquid water already contains about 33,400 H₂O molecules — just over 100,000 atoms. ρ ≈ 1 g·cm⁻³ V = (10⁻⁶ cm)³ = 10⁻¹⁸ cm³ N ≈ (10⁻¹⁸ g / 18.0 g·mol⁻¹) × 6.022 × 10²³ mol⁻¹ N ≈ 3.35 × 10⁴ molecules So a simulation box that looks microscopic on the nanometre scale can already cross the 10⁵-atom threshold before adding any solute, ions, membrane, or other components. A useful scale check for explicit-solvent molecular dynamics.

So.... is ORCA getting GPU support soon? It seems yes.

New ECCE Version available: The Extensible Computational Chemistry Environment (ECCE, pronounced "etch-ā") is a graphical user interface, scientific visualization toolkit, and data management framework for setting up, running, and analyzing computational chemistry calculations. https://github.com/FriendsofECCE/ECCE

PyFock - An efficient and fully parallelized pure python DFT and electronic structure code with GPU acceleration through just-in-time compilation https://pyfock.bragitoff.com/ Read the paper: https://pubs.acs.org/jpcafh/article/doi/10.1021/acs.jpca.6c03727/5298372/PyFock-A-Just-In-Time-Compiled-Gaussian-Basis-DFT

OPEN ACCESS https://www.nature.com/articles/s41467-026-77099-7?utm_source=chatgpt.com

ORCA (FACCTs & Max-Planck-Institut für Kohlenforschung) is a powerful quantum chemistry engine, valued for its wide range of methods, outstanding efficiency, and robustness. But modern computational workflows and Agentic AI need more than scientific breadth. They also need software that can be controlled, interpreted, and integrated programmatically. At this point, we can say: ORCA is ready! Over the past few years, ORCA's ecosystem has evolved rapidly, introducing key features such as: Machine-readable JSON output, providing structured results that can be used directly by scripts, workflow engines, and AI agents. The ORCA Python Interface (OPI), providing Python-native control for building and automating computational workflows. And extensive online documentation and tutorials, providing the knowledge layer that helps users and AI agents understand ORCA's capabilities, select and configure methods correctly, interpret workflows, and make informed decisions. All of this makes ORCA not only a powerful quantum chemistry program, but also a strong foundation for automated and agentic computational science. ORCA json manual: https://lnkd.in/eBXMFaVX OPI docs: https://lnkd.in/ePfDNhqa ORCA manual: https://lnkd.in/dzPaAMtJ ORCA tutorials: https://lnkd.in/dfGmE4wk #ORCA #QuantumChemistry #ComputationalChemistry #ScientificCompu

Fun Fact of the Day The “negative frequency” printed for a transition state is not really a vibration with a negative physical frequency. At a first-order saddle point, the Hessian has one negative eigenvalue; because the harmonic relation is effectively ω² ∝ curvature, that mode has an imaginary ω, and quantum-chemistry programs conventionally display it as a negative wavenumber. That is why the important transition-state check is not merely “one negative number,” but whether the corresponding eigenvector actually follows the intended reaction coordinate.

open access https://www.nature.com/articles/s41566-026-01946-8?utm_source=bluesky&utm_medium=social&utm_campaign=nphoton

Fun Fact of the Day One hartree is such a large molecular energy unit that, when expressed as the equivalent thermal scale Eₕ/k_B, it corresponds to approximately 315,775 K. That does not mean a one-hartree electronic excitation corresponds physically to heating a molecule to 315,775 K; it is simply the temperature for which k_BT equals one hartree. NIST tabulates the hartree–kelvin relationship among its CODATA energy conversions. For comparison, chemically important energy differences are usually tiny fractions of Eₕ: 1 kcal mol⁻¹ is only about 0.00159 Eₕ.