Timescales of Different Phenomena

Here we attempt to relate the dynamic processes, measured by time correlation functions, to their characteristic timescales in the temperature range 300-600 K, relevant to organic electronic devices operation and fabrication. It is worth mentioning that in such applications, beyond the stmctiunl dynamics treated here, the timescales associated with charge or exciton dynamics are also very important, in particular for assessing the coupling between electron and nuclear dynamics. 

In the most common case where the target is the equilibrium dynamics, the analysis has to be carried out on samples at thermal equilibrium. Albeit trivial, the above observation is not always respected in MD studies. Even in some recent papers we may find that equilibration runs limited to a few hundreds of picoseconds are often employed, although it is known that, e.g., molecular rotations relax over much longer timescales [34,119]. A possible definition of the timescale associated with a process modulating a given dynamic property, A t), is its correlation (or relaxation) time  

To recap, in this short overview we have enumerated the main dynamics phenomena driving the molecular motion and shown that their characteristic timescales can differ by several orders of magnitude depending on chemical and physical factors, preventing the definition of simple rules of thumb. 

Therefore the timescales of the phenomena of interest must be estimated on a case-by-case basis, and carefully considered in the choice of appropriate simulation techniques, models, and times, in order to avoid meaningless investigations or biased conclusions. 

---