Spectroscopic Benchmarking Science Case
The full simulation of molecular structures including the electronic structures comprises the calculation of optimized geometries, molecular orbitals, population analyses, frequencies, or optical absorptions. The combination of all these tasks as basic workflows into a meta-workflow improves the simulation enormously (see "Spectroscopic analysis"). With regard to real-life systems, the simulation has to tackle issues such as antiferromagnetic coupling between copper atoms, correct description of the coordination sphere and multiple conformations of the whole molecule. Methodologically, density functional theory is most appropriate here due to size of the system and investigated questions. Hence, the spectroscopic workflow needs to be performed several times for an array of functionals and basis sets which have to be tested for the ultimate structural and optical description with regard to experimental data.
Further, the spectroscopic meta-workflow can be combined into a new type of workflow called meta-meta-workflow with all being implemented in WS-PGRADE. Figure 8 shows four spectroscopic meta-workflows are combined into a meta-meta-workflow after performing a basic optimization. This basic optimization (basic opt WF) serves as pre-optimization step which saves calculation time in all subsequent optimizations included in the spectroscopic workflows (specX WFs). A meta-meta-workflow saves a lot of time in this application - more than a normal meta-workflow.
The spectroscopic benchmarking needs to be done for every molecule of a new class of molecules. Afterwards, the experience made in these analyses can be transferred to further members of the regarded class. This saves a lot of job definition time of the researcher.
The first input file is a opt.nw file for a basic optimisation simulation. The output of the first basic WF is a opt.out file which is parsed for the geometry by the subsequent workflows. They combine this geometry data with prepared nw-input-files for the subsequent freq, TD, Mull and solv jobs. As final output, multiple sets of output files freq.out, TD.out, Mull.out and solv.out are obtained.
Understanding of the formation of peroxo (Figure 6) and the isomeric oxo cores as well as their distinct reactivity relies on comprehensive orbital analyses. First the geometry is optimised, then TD-DFT and all other steps are performed. Figure 7 shows as example the optical spectra.
Time dependent-DFT calculated spectra predict the optical spectrum with the four LMCT bands at 340 nm, 366 nm, 381 nm and 547 nm in good accordance to the experimental spectrum.
- Herres-Pawlis, S., Hoffmann, A., de la Garza, L., Krüger, J., Grunzke, R., Gesing, S., Weingarten, N., and Terstyansky, G., Meta-metaworkflows for Combining Quantum Chemistry and Molecular Dynamics in the MoSGrid Science Gateway, IWSG 2014 (6th International Workshop on Science Gateways), June 2014, Dublin, Ireland. Accepted.
- S. Herres-Pawlis, A. Hoffmann, A. Balasko, P. Kacsuk, G. Birkenheuer, A. Brinkmann, L. de la Garza, J. Krüger, S. Gesing , R. Grunzke, G. Terstyansky, N. Weingarten, Quantum chemical metaworkflows in MoSGrid, Concurrency Computat.: Pract. Exper. 2014, in print.
- A. Hoffmann, R. Grunzke, S. Herres-Pawlis, Insights into the influence of dispersion correction in the theoretical treatment of guanidine-quinoline copper(I) complexes, J. Comp. Chem. 2014, doi: 10.1002/jcc.23706.