text: 100,129,1300831011878572032,37838307,Justin Caram,"More forays into theory from the Caram Group! Here with the Neuhauser group we show that you can use stochastic methods to rapidly study the excitonic properties of molecular aggregates. Congrats Nadine and @arundhati175 and others not on twitter :) <LINK> @arundhati175 Excitonic aggregates have two features that make them hard compared to say...semiconductors. Lots of disorder, dipolar coupling that falls of slowly (meaning tight binding misses the details). The frenkel exciton hamiltonian works ok, but requires diagonalization. @arundhati175 Since diagonalization is N^3 with system size, Its really slow for large systems, particularly 2D systems for which the system size grows with edge^2. Stochastic methods scale with NlogN (basically linearly). So much easier to screen disorder, lineshapes etc. @arundhati175 This lets us look at other cool properties...like if energy levels are correlated over any distance range, what does that do (a lot it turns out!). This is a cool application of stochastic methods that are widely used to improve DFT scaling.",https://arxiv.org/abs/2008.13228,"We show that a stochastic approach enables calculations of the optical properties of large 2-dimensional and nanotubular excitonic molecular aggregates. Previous studies of such systems relied on numerically diagonalizing the dense and disordered Frenkel Hamiltonian, which scales approximately as $\mathcal{O}(N^3)$ for $N$ dye molecules. Our approach scales much more efficiently as $\mathcal{O}(N\log(N))$, enabling quick study of systems with a million of coupled molecules on the micron size scale. We calculate several important experimental observable including the optical absorption spectrum and density of states, and develop a stochastic formalism for the participation ratio. Quantitative agreement with traditional matrix diagonalization methods is demonstrated for both small- and intermediate-size systems. The stochastic methodology enables the study of the effects of spatial-correlation in site energies on the optical signatures of large 2D aggregates. Our results demonstrate that stochastic methods present a path forward for screening structural parameters and validating experiments and theoretical predictions in large excitonic aggregates. ",Stochastically Realized Observables for Excitonic Molecular Aggregates,4,"['More forays into theory from the Caram Group!  Here with the Neuhauser group we show that you can use stochastic methods to rapidly study the excitonic properties of molecular aggregates.  Congrats Nadine and  @arundhati175 and others not on twitter :)\n<LINK>', '@arundhati175 Excitonic aggregates have two features that make them hard compared to say...semiconductors.  Lots of disorder, dipolar coupling that falls of slowly (meaning tight binding misses the details).  The frenkel exciton hamiltonian works ok, but requires diagonalization.', '@arundhati175 Since diagonalization is N^3 with system size, Its really slow for large systems, particularly 2D systems for which the system size grows with edge^2.  Stochastic methods scale with NlogN (basically linearly).  So much easier to screen disorder, lineshapes etc.', '@arundhati175 This lets us look at other cool properties...like if energy levels are correlated over any distance range, what does that do (a lot it turns out!).  This is a cool application of stochastic methods that are widely used to improve DFT scaling.']",20,08,1065