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Bernardo de Souza

@bernadsz.bsky.social

Nature lover. Curious turned scientist. Part of the ORCA development team. Now bringing Quantum Theory and Molecular Physics to the real world at @faccts-orca.bsky.social https://scholar.google.com.br/citations?user=U6szjgMAAAAJ&hl=pt-BR

176 Posts1121 Follower794 Folgt
FACCTs@faccts.de · 4mo ago

Analytical #Raman intensities are one of the notable new features of #ORCA 6.1 (MPI Kofo & FACCTs). Check the implementation paper by Frank Neese and Petra Pikulová. doi.org/10.1063/5.03... Manual on Raman simulations: www.faccts.de/docs/orca/6.... #Spectroscopy #CompChem #QuantumChem

Efficient implementation of analytical Raman intensities

In this study, we report an analytical derivative implementation of static polarizability gradients, needed for the prediction of Raman spectra, in the ORCA pro

doi.org

Bernardo de Souza@bernadsz.bsky.social · 4mo ago

If you want to combine ORCA+Python seamlessly, the OPI (ORCA Python Interface) is the way to go. The paper is out and is free of access for 6 months - it was accepted as the Editor's choice in JCCT. The interface is open-source and ready to get new contributions. 🫍🐍

FACCTs@faccts.de · 4mo ago

Our paper on the #ORCA #Python Interface OPI is published in #JCTC! pubs.acs.org/doi/full/10.... Check it out and join the OPI community. OPI on GitHub: github.com/faccts/opi OPI documentation: www.faccts.de/docs/opi/docs #FACCTs #OPI #CompChem #QuantumChem #ScientificSoftware #OpenSource

Bernardo de Souza@bernadsz.bsky.social · 7mo ago

ORCA has now 100k registered users! We are very proud to be part of the project, and all the impact it has across chemistry/physics/molecular sciences. It's really an enormous privilege to be able to help so many people execute their best ideas through our tools/theories/algorithms 🙏.

FACCTs@faccts.de · 7mo ago

What an incredible Christmas gift! The #ORCA community has reached a major milestone: 100,000 registered users. Thank you all for your trust and for being such an important part of ORCA’s journey. Your support is what makes this success possible. #ORCAqc #FACCTs #MPIKOFO #CompChem #ChemSky

100000 registered ORCA users!
Bernardo de Souza@bernadsz.bsky.social · 10mo ago

Running bad DFT calculations very fast is easy, and it's also useless. That's why we put a lot of effort in the last few years in making ORCA faster, while at the same time *increasing* the accuracy. 1/3 arxiv.org/abs/2510.197...

How Accurate Are DFT Forces? Unexpectedly Large Uncertainties in Molecular Datasets

Training of general-purpose machine learning interatomic potentials (MLIPs) relies on large datasets with properties usually computed with density functional theory (DFT). A pre-requisite for accurate...

arxiv.org

FACCTs@faccts.de · 12mo ago

Hot off the press: “A Two-Level Preconditioner for the CASSCF Linear-Response Equations” by our scientific advisor Benjamin Helmich-Paris (@orca-qc-official.bsky.social). Its already part of ORCA 6.1, check it out! doi.org/10.1021/acs.... #ORCA #ORCAqc #CompChem #QuantumChem #TheoChem #CASSCF

A Two-Level Preconditioner for the CASSCF Linear-Response Equations

We present an efficient two-level strategy to accelerate the solution of the CASSCF linear-response eigenvalue problem using a customized Davidson algorithm. By identifying a subset of important response-vector components─the so-called P space─we compute and diagonalize full Hessian and metric matrix elements while treating the remaining Q-space components with a diagonal approximation. This approach decouples the orbital and configuration responses, enabling independent preconditioning of each component. Computational cost is further reduced through the resolution-of-the-identity approximation. We demonstrate significant performance gains across a diverse set of molecules, achieving speedups of up to 2.05 compared to the standard diagonal preconditioning. The largest efficiency gains are observed for MCTDA calculations involving many excited states and relatively small response-vector lengths. The two-level strategy is available in ORCA 6.1 and paves the way for extensions to dynamic polarizabilities, which require solving large-scale linear equations, as well as to time-dependent density functional theory and CI singles.

doi.org

FACCTs@faccts.de · 12mo ago

Check out the recent paper by List, Neese et al. that ones more demonstrates the synergy of experiment and quantum chemistry powered by ORCA (DFT, GOAT, ...) @faccts.de @orca-qc-official.bsky.social doi.org/10.1021/jacs... ORCA: www.faccts.de/orca/ #ORCAqc #ORCA #Catalysis #CompChem #QuantumChem

Pericyclic Umpolung in a Catalytic Asymmetric Diels–Alder Reaction of Tropone with Enol Ethers

One remarkable feature of catalysis in chemical synthesis is its capacity to override substrate-imposed reactivity and selectivity. The inversion of normal reaction patterns, commonly known as Umpolun...

doi.org

Bernardo de Souza@bernadsz.bsky.social · 12mo ago

Update on the last post about two similar structures differing by ~ 33 kcal/mol. We split intro three fragments and saturated with Hs to check the contribution per fragment. The large total energy difference is explained trivially from a sum of the frag. contribution. 1/3 #compchem

FACCTs@faccts.de · last yr.

Check out the recent paper on Excited-state methods based on state-averaged long-range CASSCF short-range DFT by Benjamin Helmich-Paris et al. And how to use it in ORCA 6.1. doi.org/10.1039/D5CP... www.faccts.de/docs/orca/6.... #ORCAqc #CompChem #QuantumChem #ChemSky #DFT

Excited-state methods based on state-averaged long-range CASSCF short-range DFT

In the present work we propose two distinct state-averaging (SA)-based methodologies for the calculation of excited states, in conjunction with the long-range complete active space self-consistent fie...

doi.org

Bernardo de Souza@bernadsz.bsky.social · last yr.

How complicated is the conformational space of molecules? Here is a fun one I found working on something: These two structures have an RMSD of 0.45 Angs, but are **40 kcal/mol** apart in energy! I double checked, that's not a mistake, and the energy level was high. Never underestimate! #compchem

Bernardo de Souza@bernadsz.bsky.social · last yr.

The preliminary version of g-xTB from Stefan Grimme's group can already be used with ORCA 6.1. Check it out! If you find any problems, please report to the team, it is on everyone's best interest to find any bugs/issues and fix them. 🙏

FACCTs@faccts.de · last yr.

You can now use g-xTB @grimmelab.bsky.social with ORCA via the ExtOpt feature! Check out our new tutorial and learn how to use it in GOAT, NEB-TS and more. www.faccts.de/docs/orca/6.... #ORCAqc #FACCTs #gxTB #CompChem #QuantumChem

Bernardo de Souza@bernadsz.bsky.social · last yr.

The successor of GFN2-xTB, g-xTB, is out there. Brace yourselves, there is a whole new world of possibilities out there now! 🚀 Congratulations on the team, as @mrclmllr.bsky.social says, this is certainly a revolution.

Marcel M@mrclmllr.bsky.social · last yr.

After years of development and preparatory works which you might have seen on this profile, a major milestone is achieved: g-xTB marks not just an evolution, but a revolution in the capabilities of semiempirical quantum chemistry. Convince yourself! A thread. 🔗 chemrxiv.org/engage/chemr... #compchem