Q-Chem 4.4 Release Download

Last update 04/09/2017 (version 4.4.2)


Q-Chem 4.4 Manual (online , pdf file)

Click here for Q-Chem 4.4 release log

Upgrade to Q-Chem 4.4.2

Q-Chem 4.4 installation on Linux and Mac systems

Q-Chem 4.4 installation on Windows system

View and download our standard form license agreement here.


Q-Chem 4.4 Package Installation on Linux and Mac

There are two ways to install Q-Chem 4.4: using universal online installer (recommended) or downloading the complete package for offline installation.

1. Download the universal installer (recommended) for online installation.

wget -N http://www.q-chem.com/download/qcinstall/qcinstall.sh

On Mac OSX if wget is not available on your system please use curl command below:

curl http://www.q-chem.com/download/qcinstall/qcinstall.sh > qcinstall.sh
chmod +x qcinstall.sh

2. Alternatively, download the standard distribution for offline installation by selecting a package below and untar it.

tar xvf qc44.tar

To install please run the installer qcinstall.sh and follow the onscreen instruction. A detailed installation guide and step-by-step tutorials are also provided to guide you through the installation process.


After a successful installation you need to wait to receive the license file by email, and save it as


Q-Chem 4.4 Package Installation on Windows

1. Download Q-Chem installer for windows .

2. The default installation directory is c:\qchem\qc44. If you change the installation directory you need to mannually edit qcenv_s.bat file in your installation directory and specify the correct QC location in that file.

3. Start a DOS shell using the 'QChem' shortcut generated during installation or mannually clicking qcenv_s.bat in the Q-Chem installation directory, type


to generate license.data file. If you encounter error message "path not found" it is possible your QC setting in qcenv_s.bat is not correct. Please refer the previous instruction how to correct the QC setting. After completing 'qcprerun' You need to email the generated license.data file to license@q-chem.com to receive a license

4. After license is received and installed please verify the installation by running a sample calculation. Start a DOS shell from the shortlink generated during installation, and type the following command to verify.

cd qcsamples\sp
qc dft_b3lyp_h2o.in


Q-Chem Package Update and Maintenance on Linux and Mac

a) to update the installed Q-Chem to the latest distribution, run


You may need to run qcupdate.sh twice, as the first time it may update the installer script.

[Online package maintenance utility qcupdate.sh is the new added feature in 4.2 release. To upgrade pre-4.2 Q-Chem installation please download and run standard installer qcinstall.sh. ]

b) to re-generate and sumit license data, run

$QC/qcinstall.sh --update-lic

c) to receive regular Updates you can use Linux cron utility and add the line below as the cron command. Please consult your system administrator for questions about using cron.

$QC/qcupdate.sh > $QC/qcupdate.log

Q-Chem 4.4 Package Distribution

1. Please select the Q-Chem executable binary codes you wish to download:

Linux 64 Bit Parallel Code based on MPICH (recommended)

Linux 64 Bit Serial/multicore-parallel Code

Linux 64 Bit Parallel Code based on MPICH3

Mac Intel OSX 64 Bit Parallel Code (Existing MPICH2 installation is required)

Mac Intel OSX 64 Bit Serial/multicore-parallel Code

2. Please select a download type:

Standard download: for new and upgrade installations

(During installation please be sure to provide us with an accurate e-mail address when prompted for one. It is required so we can locate your account, and contact you should there be any problems with your license request.)

I agree to the terms and conditions in Q-Chem license agreement .

Q-Chem 4 Installation Guide and Step-By-Step Tutorials