Q-Chem

Software for fast and accurate simulations of molecular systems, including electronic and molecular structure, reactivities, properties, and spectra.

Q-Chem, Inc., established in 1993, is a research and development of computational software company. Q-Chem brings commercial, academic and government scientists worldwide in pharmaceuticals, materials science, biochemistry and other fields a comprehensive ab initio quantum chemistry program to solve computational problems faster, more accurately and less expensively than they could otherwise. Its capabilities range from the highest performance DFT/HF calculations to high level post-HF correlation methods. Q-Chem tackles a wide range of problems in commercial, academic and government laboratories. Q-Chem also provides users with the highest level of technical support possible.

10/08/2026

Learn more about Q-Chem's periodic boundary conditions code by watching Joonho Lee's recent webinar about QCPBC, now available on YouTube: https://youtu.be/47c0PBjAtGk

09/21/2026

Find out more about QC-PBC, our new GPW-based package for modeling materials, at this week's webinar by Joonho Lee.

Register here: https://zoom.us/webinar/register/WN_pxlGxm3KRb2fb03LhWBt7g

09/09/2026

In this recent paper, authors study the effect of pendant anionic substituents on the redox properties of ruthenium catalysts for water oxidation. They use Q-Chem's DFT and analyze the geometries and charge and spin population data using our free IQmol visualizer. https://doi.org/10.1021/acs.jpca.6c03738

Try Q-Chem 7: https://q-chem.com/try/

09/08/2026

New preprint: Spin-unrestricted linear-scaling double-hybrid DFT! Here, authors generalize their earlier linear-scaling MP2 implementation to the spin-unrestricted case, enabling asymptotically linear-scaling DH-DFT calculations for open shell and reactive molecules. https://doi.org/10.26434/chemrxiv.15008144/v1

Their linear-scaling algorithm for restricted cases is available in Q-Chem 7. Try it today: https://q-chem.com/try/

09/04/2026

In this recent preprint, authors use Q-Chem's CCSD and ezFCF to help explain their experimentally-observed high-resolution photoelectron spectra for excited TiO2 anions. https://doi.org/10.26434/chemrxiv.15007122/v1

Try spectroscopy features in Q-Chem 7: https://q-chem.com/try/

09/02/2026

The new DFT/XCIS method for valence and core-level spectroscopy was released last year in Q-Chem 6.4, and soon it will be available for open shell molecules as well! Check out this new preprint from developers, where they discuss their new implementation and apply it to accurately model spectra for a variety of open shell systems: https://doi.org/10.26434/chemrxiv.15008165/v1

Check out a webinar from the developer (Avik Ojha) here: https://youtu.be/PN-LyN2q3Vc
Try XCIS-CVS in Q-Chem 7: http://q-chem.com/try/

08/28/2026

Don't forget: The new COACH functional is now available in Q-Chem 7! COACH is a new range-separated hybrid (RSH) meta-GGA functional that strikes a balance between simplicity, accuracy, and transferability, making it ideal for a broad range of molecular systems.

Read the preprint here: https://doi.org/10.48550/arXiv.2603.23466
Try it in Q-Chem 7: https://q-chem.com/try/

08/26/2026

In this recent JCTC paper, Q-Chem developers use wavenumber power scaling (WPS) to derive scaling factors for fundamental harmonic vibrational frequencies and molecular thermodynamic corrections. They use Q-Chem to obtain geometries and frequencies with MP2, CCSD, and more than 40 different DFT functionals. https://doi.org/10.1021/acs.jctc.6c01138

Try Q-Chem 7 today: http://q-chem.com/try/

08/24/2026

New in Q-Chem 7: ECD with TDDFT! ECD enables studies of chiral molecules; Q-Chem's EOM-CC ECD can provide high-level benchmarks for medium-sized systems, while the new TDDFT implementation extends this capability to large systems.

Try it yourself in Q-Chem 7: http://q-chem.com/try/

08/21/2026

In this recent paper, authors study the low-lying ππ* excited states in five-membered ring heterocycles, approaching the problem from both MO and valence bond theory perspectives. https://doi.org/10.1021/acs.jpca.6c03644

They use Q-Chem's ADC(1), ADC(2), ADC(3), and TDDFT to model low-lying ππ* excited states in five-membered ring heterocycles, and they discuss some of the reasons why obtaining accurate results for these systems can be tricky or impossible even when using cutting-edge methods.

You can try TDDFT yourself with a free demo of Q-Chem 7: http://q-chem.com/try/

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