Wavepacket dynamics for the future: A general purpose HPC-compliant program.
Lead Research Organisation:
University of Birmingham
Department Name: School of Chemistry
Abstract
Wavepacket dynamics simulations solve the time-dependent Schroedinger equation directly and provide a visual description of a molecular system that can be easily related to high precision experiments such as laser spectroscopy and molecular beam scattering. They are, however, calculations that need large computer resources and are usually able to treat only a few (3-4) atoms. Various approximate solutions that can treat the dynamics of larger systems do exist, but usually at the cost of losing potentially crucial quantum information. A particularly powerful algorithm able to treat more than 4 atoms, yet converge on the exact result is the MCTDH method. The Heidelberg MCTDH package includes a coding of this algorithm that has already provided a number of benchmark calculations in various fields of chemical physics, particularly photochemistry. By exploiting modern computer architecture we will be able to access even larger systems, and thus push back the boundaries of computational chemistry.Computer clusters in which a number of multi-processor boards are connected together are becoming widespread in the scientific community. A computer program, however, needs to be written in a special way to take advantage of the architecture of these machines. In particular, resource-intensive parts of the program need to be parallelised . This means that different parts of the algorithm can be treated separately on different processors at the same time. The MCTDH program, however, is a serial program, executing commands one after another, and changes will need to be made to use the machines optimally. The proposed work is to update the code to treat its deficiencies. Not only will the MCTDH algorithm be parallelised to improve its efficiency, but also other methods will be implemented into the program to generate a more general code. The end result will be a program that can be used by non-specialists and that can grow with future developments in the field, in the waythat electronic structure programs such as Gaussian and Molpro can. This will move quantum dynamics forwards so that in the future much larger systems can be treated, including reactions inside proteins and in solution. These are problems which are currently well beyond the capabilities of any quantum dynamics program in existence and this would therefore represent a step change in the study of chemical reactions.
Organisations
Publications

Allan CS
(2010)
A straightforward method of analysis for direct quantum dynamics: application to the photochemistry of a model cyanine.
in The journal of physical chemistry. A

Assmann M
(2012)
9D nonadiabatic quantum dynamics through a four-state conical intersection: investigating the homolysis of the O-O bond in anthracene-9,10-endoperoxide.
in The Journal of chemical physics

Frankcombe T
(2010)
Converged quantum dynamics with modified Shepard interpolation and Gaussian wave packets
in Chemical Physics Letters

Giri K
(2011)
A full-dimensional coupled-surface study of the photodissociation dynamics of ammonia using the multiconfiguration time-dependent Hartree method.
in The Journal of chemical physics

Keß M
(2016)
Two-dimensional vibronic spectroscopy of molecular aggregates: Trimers, dimers, and monomers.
in The Journal of chemical physics

Kirkby O
(2017)
Non-radiative relaxation dynamics of pyrrole following excitation in the range 249.5-200 nm
in Chemical Physics Letters

Neville S
(2016)
Identification of a new electron-transfer relaxation pathway in photoexcited pyrrole dimers
in Nature Communications

Neville SP
(2014)
A reinterpretation of the electronic spectrum of pyrrole: a quantum dynamics study.
in The Journal of chemical physics

Penfold TJ
(2012)
Quantum dynamics study of the competing ultrafast intersystem crossing and internal conversion in the "channel 3" region of benzene.
in The Journal of chemical physics

Richings GW
(2012)
Non-resonant dynamic Stark control at a conical intersection: the photodissociation of ammonia.
in The journal of physical chemistry. A
Description | The program has been fully re-written in Fortran90 and made into modules so that it will be easier for future development to take place. This was also necessary for full use of parallel computer architectures and compilers. The program has also been expanded with a very efficient algorithm ("real wavepacket propagation") able to do scattering calculations (simulating the collisions of atoms and molecules) an order of magnitude faster than the original code. |
Exploitation Route | Quantum dynamics studies are required to understand the fine details of chemical reactivity. It is difficult to see yet how they would be used in a non-academic context as yet due to the present restrictions on the types of systems we can treat. Hopefully one day they will be as useful as classical molecular dynamics simulations in modelling materials and molecular properties, but including potentially important effects presently ignored. Presently looking at licensing issues for the software at the heart of the project. This is the first step in protecting it's use and so allowing a more widespread distribution than presently possible in its "academic only" state. |
Sectors | Chemicals |
Description | The outputs and findings have not been used outside of an academic context. |
Title | Quantics |
Description | A package for quantum dynamics simulations of molecular systems, solving the time-dependent Schroedinger equation using a variety of methods but based on the powerful MCTDH algorithm. |
Type Of Technology | Software |
Year Produced | 2015 |
Open Source License? | Yes |
Impact | This code is an update and re-write of the well-used Heidelberg MCTDH package, including many new features. It has lead to increased interest in the program and is part of an EU infra-structure project. The new direct dynamics code arising from the the project "Accurate Direct Dynamic of Non-Adiabatic systems" is to date the only fully quantum method able to treat polyatomic photochemistry and is now starting to produce results that have lead to a number of invitations to present the work at meetings. |
URL | http://stchem.bham.ac.uk/~quantics/ |