First Principles Calculation of Electron Impact Mass Spectrometry of Molecules

• Applicant: Professor Dr. Stefan Grimme
• Subject Area: Theoretical Chemistry: Molecules, Materials, Surfaces ; Organic Molecular Chemistry - Synthesis and Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2013 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 253235332

The Quantum Chemistry Electron Ionization Mass Spectra (QCEIMS) program, which as already detailed in the original proposal, combines elements of statistical theory with Born-Oppenheimer Molecular dynamics, has been successfully applied to organic molecules, and very recently to organometallic compounds and main group inorganic molecules. Six project-related publications have appeared during the first funding period, which are described briefly. The current state of the art within the QCEIMS method is then portrayed. The cost-efficient semi-empirical GFN-xTB Hamiltonian has been incorporated into the program, and the technical details are laid out. An overview of the current literature, including recent developments in statistical theory and related molecular dynamics approaches, is contained in project-related publication P4.Several extensions to the project are considered. Most importantly, we propose to modify the "QCEIMS" methodology to be suitable for the simulation of Electrospray Ionization/ Collision Induced Dissociation Mass Spectrometry (ESI/CID MS). We lay out the necessary steps and methodology that needs to be implemented. We also plan to parametrize a new, special-purpose xTB version for the fast computation of ionization potentials and electron affinities, which is a crucial step of the QCEIMS procedure. A third major point is the evaluation of computed EI mass spectra on a large experimental mass spectral database with some emphasis on non-organic systems which previously could not be treated. Applications to special chemical systems will be continued to establish QCEIMS further as a routine tool in theoretical chemistry and mass spectrometry.

• DFG Programme: Research Grants