Core-level spectra reveal a lot about valence virtual orbitals, especially for open-shell systems, but current methods often suffer from spin contamination. CVS-XCIS resolves the spin contamination issue, enabling accurate calculations for these systems. youtube.com/watch?v=PN-L...

Q-Chem provides one of the most extensive libraries for computational #spectroscopy, including: IR, UV-Vis, and vibronic spectra; X-ray spectra; restricted and unrestricted VCD; and more. Follow along this week as we discuss the latest spectroscopy developments in Q-Chem!

Join us on April 23 at 11AM PDT for a webinar from Juan E. Arias Martinez on his new ΔSCF (OO-DFT) interface in Q-Chem! It's easier to use and includes crucial analysis tools; he will also discuss how he has used it to study charge-transfer excitations. zoom.us/webinar/regi...

Q-Chem developers published a new numerical sparsity approach to local correlation for MP2; it scales competitively with (sometimes better than!) DLPNO-MP2 and will be extended to double-hybrid #DFT in QC7, providing speedup and better accuracy. doi.org/10.1021/acs....

An example of Q-Chem's #DFT in action: Authors used Q-Chem for a large benchmark study on RDB7, a large, diverse dataset containing chemical kinetics data for 11,926 reactions. Their work establishes best practices for DFT studies of reaction kinetics. doi.org/10.1039/D5CP...

The new COACH #DFT functional (developed by Liang and Head-Gordon) provides improved transferability and accuracy over existing RSH meta-GGAs, like ωB97M-V, for a wide variety of systems. Read more: arxiv.org/pdf/2603.23466

COACH will be available in Q-Chem 7, coming June 2026!

As any computational chemist who uses #DFT knows, converging SCF can be tricky. Q-Chem's “Robust SCF” algorithm provides a black-box approach that automatically detects common convergence issues and makes the appropriate corrections. Read more here: manual.q-chem.com/6.4/sub_scf_...

Text reads: "On the road to Q-Chem 7. Key Feature of the Week: Density Functional Theory. Use our vast library of functionals to model ground and excited states; Get faster results with optimized integral algorithms, RI, and great parallel performance; Improve convergence with new features like “Robust SCF”"

Density functional theory is an essential method in any #compchem toolkit. Popular and general-purpose, it allows researchers to study electronic structure, predict geometries, model spectra, and much more. Follow along this week as we talk about #DFT in Q-Chem!

In this recent paper, authors use Q-Chem's DFT alongside experiment to show that metal ions can be used as EWGs and establish a quantitative foundation for Hammett-like parameters for metal ions. doi.org/10.1021/acs....

Try Q-Chem: q-chem.com/try/

QC Lab: A Python Package for Quantum–Classical Dynamics QC Lab is an open-source Python package for quantum–classical (QC) dynamics simulations aimed to promote the development of QC algorithms, and their application to a wide variety of relevant model problems. It follows a modular design that facilitates cross-compatibility between algorithms and models. By decomposing algorithms and models into a series of tasks and ingredients that can be substituted and reused, it minimizes development efforts and code redundancy. In this Paper, we introduce the first stable version of QC Lab, and describe its design philosophy.

We just published a paper detailing our quantum–classical simulation package QC Lab in JCTC @acs.org!

This marks the release of version 1.1.1, featuring a basic interface with @qchemsoftware.bsky.social for TD-DFT calculations.

@nuchemistry.bsky.social

pubs.acs.org/doi/10.1021/...

Join us on 3/26 for our a Q-Chem webinar from Anthuan Pérez (Universität des Saarlandes)! He will be discussing his recent work with projection-based CC-in-DFT methods in Q-Chem, which he uses to model static polarizabilities of solvated organic molecules. zoom.us/webinar/regi...

Computation of Partial Auger Decay Widths from Complex-Valued Equation-of-Motion Coupled-Cluster Energies We discuss the computation of partial Auger decay widths with equation-of-motion ionization-potential coupled-cluster (EOMIP-CCSD) theory in the framework of non-Hermitian quantum mechanics (NHQM). In NHQM, the decaying character of metastable states is described with complex energies and the total decay width is obtained directly from the total energy. In contrast, the computation of partial decay widths, i.e., the contributions of different decay channels to the total width, requires further analysis. However, partial widths are important for Auger spectroscopy as they determine the probability with which different final states are formed and hence the shape of the Auger spectrum. Recently, we introduced Auger channel projectors (ACPs), which selectively remove decay channels from the EOMIP-CCSD excitation manifold. This method requires a separate EOMIP-CCSD calculation for each decay channel. Here, we suggest an alternative: We solve the EOMIP-CCSD equations for the core-ionized state in the full excitation manifold and decompose the imaginary part of the resulting energy. In this way, we obtain all partial decay widths at once. We compute Auger spectra for K-edge-ionized states of methane, ethane, and hydrogen sulfide, and a Coster–Kronig spectrum for L1-edge-ionized hydrogen sulfide. The results obtained with our new approach differ only negligibly from ACP results. We also present the first Auger spectra for the cyanide anion, including vibrational broadening, and discuss the differences between the spectra of the carbon core hole and the nitrogen core hole.

Check out the latest paper from Q-Chem developers at KU Leuven, in which they present a new method for computing partial Auger decay widths faster and more robustly! doi.org/10.1021/acs....

Follow us to stay up-to-date on new features and papers from Q-Chem developers!

Congratulations to researchers at CSU Fullerton on their recent paper! They develop descriptors for photoacidity and photobasicity; they use several Q-Chem capabilities (including DFT and libwfa) in their work. doi.org/10.1021/acs....

Try Q-Chem today: q-chem.com/try/

Check out this recent preprint! Authors present benchmarks of several SF-TDDFT variants and assess the efficacy of each for modeling strongly correlated systems. They use Q-Chem's SF and SA-SF. doi.org/10.26434/che... #compchem #DFT

Try Q-Chem: q-chem.com/try/

In this recent paper, authors introduce a new geometrical descriptor for covalency. They use Q-Chem's EDA, a well-established descriptor for covalency, as a point of comparison for their new metric. doi.org/10.1039/D5DT...

Try EDA in Q-Chem: q-chem.com/try/

In this recent work, authors study the interplay of several factors in the stability of cyclacenes, using Q-Chem's TAO-DFT to accurately capture the strong correlation. doi.org/10.1002/jcc....

Try TAO-DFT in Q-Chem 6.4: q-chem.com/try/

In this recent preprint, Q-Chem developers use Q-Chem as the back-end driver for open-source code Fragme∩t to do large-scale fragment-based predictions of protein-ligand interactions! Read more here: chemrxiv.org/doi/full/10....

Try Q-Chem: q-chem.com/try/

Exploring the Isomer Landscape, Fragment Additivity, and Vibrational Signatures of the Z-Alanine Protected Amino Acid Derivative The N-benzyloxycarbonyl-l-alanine molecule is a derivative of the l-α-alanine amino acid with a benzyl carbamate protecting group at the N-terminus, more commonly denoted Cbz-Ala or Z-Ala. In this computational investigation, we sought to determine the available isomers of Z-Ala and their distinguishing spectroscopic signatures via quantum-chemistry methods. Sixty-five total isomers were obtained, and coupled-cluster- and perturbation-theory-based relative energies were computed. The two nearly degenerate, lowest-energy isomers were found to differ in their configuration than the lowest-energy form of isolated alanine, suggesting that the protecting group changes the dominant form of Ala. Through comparisons to exhaustive sampling of Ala and benzyl formate isomers, nearly all of the Z-Ala structures could be ascribed to fragment-paired structural motifs, with a few outliers exhibiting new intramolecular interactions between the constituent fragments. Based on this observation, an assessment of the additivity of the two fragments’ relative energies was performed for Z-Ala energies. Many of the isomers’ energies were reasonably described by such considerations, although backbone strain and hydrogen-bonding interactions altered this energy landscape and led to nonadditive effects for several of the isomers. Comparison to experimental REMPI-based UV/IR ion-dip vibrational spectra in the 90–1822 cm–1 region indicated that two isomers are dominantly present at the experimental conditions, although signatures of other isomers from the ensemble were also observed. Clear assignments of structural motifs were possible through this experimental comparison. Computed coupled-cluster benchmarks allowed for methodology assessments in this study. The modified opposite-spin MP2 method (MOS-RI-MP2) was found to be particularly accurate, relative to these benchmarks, after minor adjustment of the range-separation parameter. Density functional theory (DFT) methods were found to be variable in their accuracy for both energies and spectra, although a few key functionals performed particularly well for this system in the low-frequency region of the vibrational spectrum. These methodology constraints provided recommendations for similar systems and subsequent anharmonic analyses.

In this new paper, authors determine over sixty isomers of Z-Ala and study their spectroscopic signatures. They use Q-Chem for ab initio simulations with 144 DFT functionals, CCSD, and PT (RI-MP2, MOS-MP2, and MP2.5). doi.org/10.1021/acs....

Try Q-Chem: q-chem.com/try/

Transition State Model for the Manganese-Based Chemical Hydrogen Battery Transition state modeling is a powerful tool for unraveling the mechanistic intricacies of chemical reactions. It plays a pivotal role in the design of innovative catalytic systems, facilitating progress in the field of catalysis. A carbon-neutral chemical hydrogen battery is the most relevant approach for the storage and transportation of hydrogen fuel. Herein, with the aid of transition state models, we decipher the mode of activity of the pincer-ligated manganese complex that enables the reversible hydrogenation and dehydrogenation process for the efficient H2 storage and release. We identified the critical contributions from the basic amino acids, specifically lysine and its potassium salt, as well as the influence of solvent, counterions, and water, in governing the reversibility. In addition, we have probed into the role of noncovalent interactions during the capture and release of CO2 by potassium lysinate, thereby enabling the realization of a carbon-neutral chemical hydrogen battery system.

In this recent paper, researchers study carbon-neutral storage and release of H2, using Q-Chem's second-generation EDA for an in-depth exploration of the interaction energies of transition states. doi.org/10.1021/acsc...

Try ALMO-EDA in Q-Chem: q-chem.com/try/

The videos from the Q-Chem workshops last week at the Virtual Winter School on #CompChem are posted! If you missed us, you can watch the talks and work through the exercises here: winterschool.cc/program/day-...

Don't forget, Q-Chem has two VWSCC workshops happening over the next 24 hours: One at 9am CET, and another at 10pm CET! Join whichever fits your timezone best. Register here: winterschool.cc

2026 Nick Besley and Michael Wormit Award nominations are due this week! If you know someone who develops in Q-Chem or works with computational spectroscopy methods, please consider nominating them.

Wormit Award: q-chem.com/about/wormit/
Besley Award: q-chem.com/about/besley/

Don't forget about the 2026 Virtual Winter School in Computational Chemistry (VWSCC) meeting, happening next week! This is a great (free!) opportunity to learn and network, including talks and hands-on workshops! Learn more and register here: winterschool.cc #compchem

Don't forget about the upcoming Q-Chem webinar from Avik Ojha; he will discuss his recent work implementing X-ray spectroscopy features in Q-Chem (including XCIS-CVS, which is now available now in Q-Chem 6.4)! Register here: zoom.us/webinar/regi...

Don't miss next week's webinar from Q-Chem developer Avik Ojha (OSU), who will be talking about his recent CVS-XCIS implementation in Q-Chem for X-ray spectroscopy modeling. Read the abstract and register here: zoom.us/webinar/regi...

Q-Chem is thrilled to be one of the sponsors for the 2026 Virtual Winter School on Computational Chemistry! This year's schedule includes many exciting lectures and hands-on workshops, including a Q-Chem workshop. Learn more and register: winterschool.cc #compchem

Happy New Year! As we enter 2026, we want to celebrate the accomplishments of the Q-Chem community over the past year. Check out our 2025 Year In Review publications list: q-chem.com/news/2025-qc...

Thanks to all of our users and developers for making Q-Chem possible! ✨💫

Webinar 84: Modern Quantum Chemistry in Q-Chem 6.4 YouTube video by QChemSoftware

Did you miss the recent Q-Chem 6.4 launch event? Not to worry! Watch this webinar recording from John Herbert to learn about our latest release, including a variety of exciting new features: youtu.be/PXMXKPXd8Ok

Try Q-Chem 6.4: q-chem.com/try/

Q-Chem 6.4 includes Robust SCF: A simple black-box approach for improved convergence! It automatically detects and corrects common SCF convergence issues, including plateauing, oscillation, and unstable solutions. manual.q-chem.com/6.4/sub_scf_...

Try Q-Chem 6.4: q-chem.com/try/

In Q-Chem 6.4: Stochastic RI-CC2 analytical gradients and derivative coupling! Obtain accurate CC2 gradients faster, with O(N4) scaling with basis set size. Check out the recent preprint from developers:
doi.org/10.48550/arX...

Try Q-Chem 6.4: q-chem.com/try/