Nonadiabatic molecular dynamics simulation for carrier transport in a pentathiophene butyric acid monolayer

Abstract

We present a new approach to carry out non-adiabatic molecular dynamics to study the carrier mobility in an organic monolayer. This approach allows the calculation of a 4802 atom system for 825 fs in about three hours using 51,744 computer cores while maintaining a plane wave pseudopotential density functional theory level accuracy for the Hamiltonian. Our simulation on a pentathiophene butyric acid monolayer reveals a previously unknown new mechanism for the carrier transport in such systems: the hole wave functions are localized by thermo fluctuation induced disorder, while its transport is via charge transfer during state energy crossing. The simulation also shows that the system is not in thermo dynamic equilibrium in terms of adiabatic state populations according to Boltzmann distribution. Our simulation is achieved by introducing a linear time dependence approximation of the Hamiltonian within a fs time interval, and by using the charge patching method to yield the Hamiltonian, and overlapping fragment method to diagonalize the Hamiltonian matrix.

Plasmon-in-a-Box: On the Physical Nature of Few-Carrier Plasmon Resonances

“…Until this high density limit is reached, there exists a rather extended intermediate density regime 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 20 treatments through ab-initio 37 and molecular dynamics methods 38 …”

Charge Carrier Localization and Transport in Organic Semiconductors: Insights from Atomistic Multiscale Simulations

“…[ 53 ] The importance of thermal disorder in small molecule based organic crystals is now well appreciated [ 33 ] and will be only briefl y discussed here. [ 38,64 ] [ 33,62,63 ] In Figure 1 b,c (top panel) we present the DOS and the localization length for such a system consisting of 100 sites, obtained by averaging over 25 000 realizations of the system, with atomic displacements from the Gaussian distribution with standard Adv.…”

“…An approach that transparently takes into account the dynamic localization of carriers combines classical MD with time propagation of the Schrodinger equation according to the Hamiltonian that depends on atomic coordinates obtained from MD. One should also note that Ehrenfest dynamics is known to suffer from the issue that the mean energy of carriers is substantially larger than the correct one, [ 38,94 ] Fewest switches surfaces hopping method is a modifi cation of Ehrenfest dynamics that solves this issue. In simulations based on Ehrenfest dynamics, [ 33 ] experimentally observed trend of mobility that decreases with increasing temperature was obtained.…”

“…[ 33,93 ] This approach is referred to as Ehrenfest dynamics. [ 95 ] In simulations based on this approach [ 38 ] with the Hamiltonian obtained from CPM, it was found that the transition from one adiabatic state to another takes place when the two adiabatic states cross each other and that these transitions dominantly determine the carrier transport. Given the presence of localization of band edge states (and delocalization of states further away from the band edge), this trend is something that may not be expected since higher temperature should promote the carriers from localized to delocalized states and improve the transport.…”

Generalized Kinetic Monte Carlo Framework for Organic Electronics

“…With the rising amount of computational power and powerful clusters, investigations on the detailed structure of organic materials and their influence on the physical properties using molecular dynamics (MD) have gained rising interest in the community [40][41][42]. This raises the demand of a generalized lattice representation for kMC studies [6,[43][44][45].…”