Chronus Quantum

Unconventional and Explicitly Time-Dependent
Electronic Structure Theory

What is Chronus Quantum?

Chronus Quantum is an ab initio computational chemistry software package that focuses on explicitly time-dependent and unconventional post-SCF quantum mechanical methods.


The beta release of Chronus Quantum will ship with many great features. New features will be added as we work towards a release version. A list of current and soon-to-come features are listed below.


  • Restricted Hartree-Fock (RHF)
  • Unrestricted Hartree-Fock (UHF)
  • Constrained Unrestricted Hartree-Fock (CUHF)
  • Commutator Direct Inversion in an Iterative Subspace (CDIIS) Optimization Acceleration
  • RHF Real-Time Propagation
  • UHF Real-Time Propagation
  • Configuration Interaction Singles (CIS)
  • Particle-Hole Random Phase Approximation (ph-RPA / TDHF)
  • Ground State Electric Multipole Moments
  • Excited State Electric Multipole Moments
  • Oscillator Strengths (within the Dipole Approximation)
  • Superposition of Atomic Densities Initial SCF Guess

Coming Soon

  • Harris Functional SCF Guess
  • Natural Molecular Orbitals (NO)
  • Natural Transition Orbitals (NTO)
  • Energy Specific Davidson Algorithm
  • Standard Frequency Dependent Linear Response
  • Damped Frequency Dependent Linear Response
  • Particle-Particle Random Phase Approximation (pp-RPA)

In the Works

  • Two-Component Spinors (2CS)
  • 2CS Real-Time Propagation
  • Douglas-Kroll-Hess (DKH) Two-Component Relativistic Spinors
  • Determinant Configuration Interaction (CI)
  • Graphical Unitary Group Approach (GUGA) to CI
  • CI Real-Time Propagation
  • Complete Active Space (CAS) Methods
  • CAS Real-Time Propagation
  • Density Functional Theory
  • Ground State Magnetic Multipole Moments
  • Excited State Magnetic Multipole Moments
  • Møller-Plesset Perturbation Theory
  • Coupled Cluster (CC)
  • Equation-of-Motion Coupled Cluster (EOM-CC)
  • CC Real-time Propagation
  • EOM-CC Real-time Propagation


  • Ability to utilize Gaussian Formatted Checkpoint (FCHK) files
  • Ability to utilize Gaussian Unformatted Raw Matrix Element files
  • COMING SOON: Interface to Psi4

Get the Beta Version!

We are pleased to announce that the Beta version of Chronus Quantum is now available on GitHub. All are encouraged to obtain a copy of the code to aid in the open source, community-driven development of the Chronus Quantum software package.

To obtain a copy of the code, please go to the Li Research Group GitHub Page to obtain a git clone link or download the tar file under the releases tag. Currently Chronus Quantum only supports builds on GNU/Linux systems with the GNU compiler suite. Other build combinations (such as OSX or Intel Compilers) have not been tested and will not be supported by the developers at this time.

Cloning Chronus Quantum From The Command Line

To clone the Chronus Quantum GitHub Repository, you may use the following command on a GNU/Linux machine with git installed:

> git clone