Q-Chem

WebMO 25 is now available! It has a variety of new, exciting features that make its web-based interface to computational chemistry packages even better—and best of all, it now includes support for our latest release, Q-Chem 6.3!

Run calculations for free on their demo server: webmo.net/demo/

Effects of Conformational Sampling on Computing Redox Properties Using Linear Response Approach Redox processes are an important step in many chemical and biochemical reactions. One simple approach to calculate the free energy change of a redox process is linear response approximation (LRA). However, variability in conformational and energy-gap sampling poses a challenge in balancing computational cost and accuracy. Herein, we calculate the redox properties of the one-electron oxidation processes for small, biologically relevant redox-active molecules (e.g., phenol, phenolate, benzene, indole, lumiflavin) in aqueous solution using two conformational sampling strategies. We sampled the conformations using molecular mechanics (MM) and hybrid quantum mechanics/molecular mechanics (QM/MM) simulations to investigate how these techniques affect redox properties. We also performed QM/MM energy-gap sampling while varying the QM region to investigate its impact on overall redox behavior. We observed free energy of oxidation, and consequently, oxidation potential differs consistently by ∼0.2–0.4 V between QM/MM and MM sampling for the molecules under investigation. Overall, we infer that computationally cheaper MM sampling would be adequate for computing the redox properties of small molecules when corrected by a system-specific correction factor.

In this recent work, researchers compare MM and QM/MM approaches to conformational sampling for the calculation of redox properties. They use Q-Chem for the QM/MM single-point energy calculations.

S. Maity, R. Sarangi, and A. Acharya. J. Phys. Chem. B. 2025.
doi.org/10.1021/acs....

Graph Convolutional Neural Network-Enabled Frontier Molecular Orbital Prediction: A Case Study with Neurotransmitters and Antidepressants With the advancement of artificial intelligence-embedded methodologies, their application to predict fundamental molecular properties has become increasingly prevalent. In this study, a graph convolut...

Researchers use a #neuralnetwork to study how the chemical hardness of neurochemicals relates to their affinities for neuroreceptors, specifically focusing on neurotransmitters and antidepressants. They use Q-Chem for their #DFT calculations. doi.org/10.1021/acs....

Join us on July 31 at 11AM for our Nick Besley Award Webinar! The webinar will be presented by award winner Prof. Justin Talbot; he will be discussing his recent work on developing methods for studying excited state potential energy surfaces. Register: zoom.us/webinar/regi...

Q-Chem was honored to be one of the sponsors of the 2025 MERCURY Conference at UPitt last week! We were excited to hear the multitude of ways that many of these students and professors are using Q-Chem in their ongoing research work. Thanks to those who stopped by!

Revisiting a large and diverse data set for barrier heights and reaction energies: best practices in density functional theory calculations for chemical kinetics Accurate prediction of barrier heights and reaction energies is of paramount importance for reaction kinetics. For computational efficiency, such calculations are typically performed with density func...

"This workflow provides crucial insights into when Kohn-Sham DFT and even gold-standard CCSD(T) may be unreliable, particularly in the presence of strong static correlation."

Read the paper: doi.org/10.1039/D5CP...
Try Q-Chem for free: q-chem.com/try/
(4/4)

"We propose our orbital stability analysis-based 3-tier classification workflow as a best-practice protocol for DFT calculations in chemical kinetics." (3/4)

"By analyzing spin-symmetry breaking at both the SCF and κ-OOMP2 levels, we classified reactions based on the nature and extent of electron correlation, traced key sources of error, and addressed them to the degree possible." (2/4)

Text reads: "Revisiting a large and diverse data set for barrier heights and reaction energies: best practices in density functional theory calculations for chemical kinetics. Xiao Liu, Kevin A. Spiekermann, Angiras Menon, William H. Green, and Martin Head-Gordon. PCCP. May 2025."

Congratulations to Q-Chem developers and collaborators on their PCCP Hot Paper!

From author Xiao Liu: "In this work, we present a thorough investigation into the unexpectedly large RMSDs for the ωB97X-D3 functional previously reported on the RDB7 dataset (~12,000 reactions)..." (🧵1/4)

This week, we featured papers that used various Q-Chem features, including TD-DFT with SOC, X-ray spectroscopy, CAP-EOM-EA-CCSD, and efficient gradients for localized diabatic state energies and couplings. Want to try these yourself? Request a free trial: q-chem.com/try/

Authors investigate electron scattering in nitrous oxide, using Q-Chem's CAP-EOM-EA-CCSD and ezFCF to explain features of the experimentally-observed experimental two-dimensional electron energy loss (EELS) spectra. doi.org/10.26434/chemrxiv-2025-m5dnl

Only one week until our Q-Chem User Workshop, happening in Pittsburgh, PA! Don't miss talks from the Q-Chem team, including an introduction to our free visualizer IQmol, DFT and spectroscopy modeling, and new features in Q-Chem 6.3. Register here: q-chem.com/news/2025-pi...

In this recent paper, Q-Chem developers calculate gradients of localized diabatic state energies and couplings at minimum cost. Their approach provides significant savings, benefitting researchers studying electronic relaxation and electron transfer. doi.org/10.1063/5.02...

Did you know that Q-Chem's TD-DFT engine has spin-orbit coupling? Calculate L- and M-edge X-ray and XUV spectra at very low cost! doi.org/10.1039/D5CP...

Have you heard about our upcoming workshop? It's not too late to sign up! This beginner-friendly workshop utilizes our free IQmol server and is open to all experience levels, whether or not you are currently a Q-Chem user. Register here: www.q-chem.com/workshops_re...

Text reads: Nuclear–Electronic Orbital ab initio Wave Function Methods in Q-Chem. Jonathan Fetherolf, Princeton University July 17 — 10:00AM PDT

Don't miss our next Q-Chem webinar, Nuclear–Electronic Orbital ab initio Wave Function Methods in Q-Chem, happening on July 17th at 10AM PDT! View the abstract for the talk and register here: zoom.us/webinar/regi...

Text reads: Probing “hydridic hydrogen bonds” using energy decomposition analysis based on absolutely localized molecular orbitals David W. Roberts and Yuezhi Mao. Phys. Chem. Chem. Phys. June 2025.

In this recent paper, Q-Chem's EDA is used to study hydridic hydrogen bonding, allowing researchers to gain useful physical insights into the nature of the bonding and the causes of observed spectral shifts. doi.org/10.1039/D5CP...

Request a free trial: q-chem.com/try/

Pittsburgh skyline with text reading: Q-Chem User Workshop. July 23, 9AM-1PM. Explore new features, hear from experts, and learn practical strategies for running fast, accurate molecular simulations with Q-Chem!" (Photo credit: Tyler Rutherford, Unsplash)

Join us for our next in-person Q-Chem User Workshop, happening on July 23 from 9:00 AM—1:00 PM at the University of Pittsburgh! Register here: q-chem.com/workshops_re...

Text reads: "Towards control in Suzuki-Miyaura CTCP – the synergy between water and RuPhos" Siebe Detavernier, Florian Matz, Julien De Winter, Pascal Gerbaux, Thomas-C. Jagau, Guy Koeckelberghs. European Polymer Journal. June 2025.

This recent collaborative work from Q-Chem developers and colleagues explores Pd(RuPhos)-catalyzed polymerization, using both theoretical and experimental approaches to study two opposing mechanisms. doi.org/10.1016/j.eu...

Request a free trial of Q-Chem: q-chem.com/try/

Images of Shirin Faraji, Roi Baer, and Andreas Dreuw above text that reads: "Congratulations to Q-Chem developers Shirin Faraji, Roi Baer, and Andreas Dreuw on their election to the board of WATOC!"

Congratulations to Q-Chem developers Shirin Faraji, Roi Baer, and Andreas Dreuw on being elected to the board of WATOC! We are thrilled to have these researchers as part of our community and excited to see their ongoing contributions to the field of theoretical chemistry.

Text reads: "Effect of Hydrostatic Pressure on the g Tensor and Hyperfine Coupling Constants of the Nitroxide Radical Characterized by Ab Initio Calculations. Ana Gurgenidze, Anna I. Krylov, Susumu Takahashi. J. Phys. Chem. Lett. June 2025."

In this paper, authors study the effects of hydrostatic pressure on magnetic spin parameters of the nitroxide radical, using Q-Chem to optimize molecules under pressure and predict magnetic properties. doi.org/10.1021/acs....

Request a free trial: q-chem.com/try/

Farewell to #WATOC2025! Thanks to those who stopped by our booth, and congrats to Yannick Calvino Alonso, winner of our giveaway. We are honored to have had the opportunity to learn from many brilliant researchers and hear about exciting science from groups across the globe!

It's the last day of #WATOC2025, and we're delighted to highlight the plenary talk from Q-Chem developer Thomas Jagau on his work with complex-energy electronic-structure methods!

Also be sure to swing by the posters of some of these Q-Chem developers during Poster Session 3 this evening at #WATOC2025!

Florian Matz
Madhubani Mukherjee
Anthuan Ferino Pérez
Charlotte Titeca
Cansu Utku

Some exciting talks from Q-Chem developers are happening this morning at #WATOC2025 (06/26):

Thomas Froitzheim (B1, 8:30AM)
∆g-xTB: Excited states with state-specific extended Tight-Binding

Lin Lin (A1, 8:30AM)
Finite-size error in quantum chemistry methods for periodic systems

Text reads: "New in Q-Chem 6.3: PV Model for Elevated Pressures. Using Conformational Sampling to Model Spectral and Structural Changes of Molecules at Elevated Pressures. Felix Zeller, Phillip Pracht, Tim Neudecker. JPC A. February 2025."

These researchers introduce a new model (PV) to simulate molecules under pressure, allowing them to study pressure-induced structural and spectroscopic changes. Their method is now available in Q-Chem 6.3! pubs.acs.org/doi/10.1021/...

Request a free trial: q-chem.com/try/

Don’t miss these posters from Q-Chem developers in Poster Session 2 at #WATOC2025:

Rachel Stein
Computing Hydrogen Tunneling Splittings with Nuclear-Electronic Orbital Multireference Configuration Interaction

Manuel Hodecker
Conformer Ensemble Processing for Improved NMR Spectrum Prediction

Make sure to stop by posters from these Q-Chem developers during Poster Session 1 on Monday evening! #WATOC2025

Nicola Bogo
Wenjie Dou
Lisa Hetzel
Alessandro Mangiameli
Kaushik Nanda
Felix Plasser
Chongxiao Zhao

Don’t miss these talks from Q-Chem developers at #WATOC2025, happening on Monday (06/23):

Debashree Ghosh (Session E1, 08:30AM)
Structure and photophysics of melanin

Christopher Stein (Session B2, 11:10AM)
Simple Embedding Models for Metallic Surfaces

Attending #WATOC2025? If so, stay tuned! We'll be posting each day of the conference with a list of exciting talks and posters from current and former Q-Chem developers.