Quantics Direct Dynamics MPI and OMP code

Purpose of Module

The module focuses on improving the parallel version of Direct Dynamics variational multi-configuration Gaussian wavepacket (DD-vMCG) method. At every step of the Direct dynamics propagation, the energies, gradients and hessians are evaluated at the center of each gaussian wavepacket by calling an external program. One of the challenge of Direct Dynamics is the cost of computation for the evaluation of the potential energy surfaces. The electronic structure calculations are performed for each gaussian wavepacket individually and thus, parallelizing the call to the electronic structure method greatly decreased the time of computation between each nuclear step. There is already an existing OpenMP parallelization of the code and the purpose of this module is to add an extra MPI layer to it to allow affordable simulation of large system by spreading the calculations across multiple computation nodes. The module has been added and tested within the Quantics quantum dynamics package which is available on Gitlab.

Background Information

The latest version of quantics package and the code developed related to this module within the Quantics software package are merged and available through Quantics.gitlab.


This module will be extensively used in the near future to study the photochemistry of large systems, whose size limited the application of the previous version of the DD-vMCG code.


After Quantics code has been successfully installed. The Quantics README file will help you to install the Quantics code. All the tests available for Direct Dynamics are suitable to test this module and can be found at inputs/. A good example to test the MPI version of Quantics is butatriene . After you have copied the but_dd.inp file in inputs/butatriene and the but_dddata directory, the test can be done through the following command:

$ mpirun quantics.mpi -mpi test.inp

The following command should be in case the code is compiled with both OMP and MPI:

$ mpirun quantics.mix -mpi test.inp

Source Code

The source code for this module can be found within the Quantics software which can be downloaded via Quantics.gitlab. You firstly need to make an account (gitlab). The quantics project has a private repository so you also need to ask for access by emailing Graham Worth (g.a.worth@ucl.ac.uk). In order to clone it into your computer, then type:

$  git clone https://gitlab.com/quantics/quantics.git