Montag, 19. Juni 2017

Q-Chem 5.0 with ADC/SS-PCM has been released!

While I'm still in the process of writing the second post about boron-subtituted aromatics, let me quickly mention that Q-Chem 5.0 has recently been released. 

Why is this special, you may ask? It is, because it contains the ADC/SS-PCM approach that I have developed during my PhD and that has been discussed numerous times in this blog. With this approach, you can accurately model your favourite excited states and transitions from (emission) and to (absorption) them in solution at the ADC level of theory at up to third order in perturbation theory, i.e., ADC(3), a very accurate benchmark method.
You can also employ e.g. the very efficient riSOS-ADC(2) approach and investigate quite large molecules (say: materials) with up to 500 basis functions. Since ADC is, in contrast to TD-DFT, an ab-initio method, it does provide complete and physically sound description of the electrostatics of the systems as well as its interaction with the solvent/dielectric environment. We compared the ADC2/SS-PCM and ADC3/SS-PCM approaches already in the publication presenting the method.

I'm currently in the final steps of publishing another article about a project with my friend and colleague Felix (find his blog in the menu), which turned out to be a nice showcase for the model. Turns out I just made this table-of-contents graphic, which I want to share with you:

It shows the excitation-hole (in blue) and excited electron (in red) of the lowest excited singlet state (S1) of an already quite large push-push system that we studied in the article. In the top left corner, it shows the excited electron computed with the SS-PCM simulating the non-polar solvent cyclohexane, and in the bottom right corner with parameters for the polar solvent acetonitrile. From this quite intuitive visualization it becomes clear how the electron-hole or in other word charge separation (the distance between the blue and red blops) increases as it is stabilized by the polar solvent and, more importantly, how this affects the properties of the system. I'll post a link to the article as soon as it appears online.

A brief description of the theory behind the ADC/SS-PCM model and its capabilities can be found in the Q-Chem 5.0 online manual, which you can find here.

Please note that very unfortunately, due to a last minute change of some defaults of the PCM solvent model that was not communicated very well, the description of ADC/SS-PCM in the in the manual is incomplete concerning one detail: For all calculations with the model the line "ChargeSeparation Marcus" has to be included in the $pcm block of the input file. This bug will be fixed with the next release (5.0.1) in July.

So long,
Jan


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