CMSP Seminar (Atomistic Simulation Webinar Series): The Multiconfiguration Time Dependent Hartree (MCTDH) Approach and Applications in Gas Phase and Condensed Phase Chemistry
Starts 6 May 2020 11:00
Ends 6 May 2020 12:00
Central European Time
The most appropriate way of studying microscopic systems is by following a purely quantum mechanical approach. If for the dynamics of electrons it is not recommended to follow a classical description, the dynamics of nuclei (ions) which are a few order of magnitude heavier can often be described with enough accuracy classically: the quantum effect can then be recovered using approximate approach inspired from the Feynman Path integral description of quantum mechanics. Ideally, one would want to treat the dynamics of the nuclei quantum mechanically by solving the Schrödinger equation. Unfortunately, this treatment suffers from what is known as the ‘curse of dimensionality’ which is the exponential increase in complexity of the problem with its size: an issue that currently limits the full quantum mechanical treatment of microscopic system with standard procedures to molecules with 4 to 5 atoms. In the early 90s, among various efforts to overcome those limitations, the multiconfiguration time dependent Hartree1 (MCTDH) approach was introduced by the theoretical chemistry group in Heidelberg. This method with many improvements that happened throughout the years made it possible to treat some biological molecules2 (with up to 256 degrees of freedom) quantum mechanically and opened the possibility of a fully quantum mechanical study of condensed phase systems.
In this talk we will present the MCTDH method by focusing on some of its core equations, its benefits and its limitations. We will also describe some of the recent advances which allow to study efficiently more complicated molecular systems. Then we will discuss some recent projects of interest where an extensive use of the MCTDH was made. Those will range from the calculation of absorption cross-sections of ozone in order to understand the ozone isotopic anomaly3 (which is of interest in atmospheric chemistry) to the calculations of the infrared spectrum of water clusters or the scattering of water on a nickel surface. We will conclude by discussing some perspectives of the usage of the MCTDH approach in condensed phase physics.