I would like to request access to medium level computational resources for work on the photophysics of triplet-triplet annihilation upconversion (TTA-UC) systems. TTA-UC systems are multi-component and have several properties, such as the packing and triplet energy, that are challenging to assess experimentally. Therefore, it is highly motivated to model the systems computationally, from the bulk material scale to the electronic structure of individual sensitizers and annihilator molecules. Material-scale TTA-UC will be modelled with Monte-Carlo simulations in Matlab and will be managed primarily by my postdoctoral fellow Dr. Krishnapriya Kunumma. More information about the use of the code can be found in our recent publication: Carrod, A. J.; Berghuis, A. M.; Gopalakrishnan, V. N.; Monkman, A.; Danos, A.; Börjesson, K. Separating triplet exciton diffusion from triplet–triplet annihilation by the introduction of a mediator. Chem. Sci. 2025, 16 (3), 1293-1301, 10.1039/D4SC07004F. Constructing a TTA-UC system for Monte Carlo simulations is computationally intensive due to long triplet lifetimes, the need for large system volumes for statistical stability, extensive particle-interaction tracking and high sampling demands for converging photophysical observables. Energetics of organic molecules and dimers will be evaluated with TD-DFT calculations, mainly in Gaussian and Orca, where we will study small diketopyrrolopyrrole-based molecules and possibly other dyes of 20-60-atom-size. Intermediate-size systems (~ 104 atoms for pure MM) will also be modelled with molecular mechanics, where we are currently looking at the LAMMPS software. My PhD student Hannah Tideland will be the person performing these calculations. Both students have experience with performing calculations with the methods mentioned above, and they are both part of our current computational resource project “Spirocarbons in TADF systems”. Based on our experience of the soon-to-expire small allocation and given the more extensive simulations planned in the next stage, we think that a medium resource allocation would be best suited to meet our needs.