How to calculate charge mobility in molecular materials from surface hopping non-adiabatic molecular dynamics – beyond the hopping/band paradigm

Carof, Antoine; Giannini, Samuele; Blumberger, Jochen

doi:10.1039/c9cp04770k

Cited by 39 publications

(62 citation statements)

References 98 publications

(99 reference statements)

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“…Here we only describe in some detail the decoherence correction used and refer to ref. [32] for a detailed description of trivial crossing detection and elimination of spurious long‐range charge transfer algorithms. The decoherence correction is based on exponential damping of all except the active band states (

j \neq a

c_{j} \to c_{j} \exp false(- normalΔ t / τ_{j a} false)

.…”

Section: Methodsmentioning

confidence: 99%

“…These algorithmic advances improve a number of desirable properties of FOB‐SH including Boltzmann occupation of the band states in the long time limit, internal consistency between charge carrier wavefunction and surface populations of the band states, and convergence of charge mobility with system size and nuclear dynamics time step. [ 32 ] We refer to the Experimental Section for a specific discussion of the multiple time step algorithm as well as a more efficient propagation of the electronic Schrödinger equation introduced in this work to deal with large systems.…”

Section: Figurementioning

confidence: 99%

“…[14] the band states, and convergence of charge mobility with system size and nuclear dynamics time step. [32] We refer to the Experimental Section for a specific discussion of the multiple time step algorithm as well as a more efficient propagation of the electronic Schrödinger equation introduced in this work to deal with large systems.…”

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confidence: 99%

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Flickering Polarons Extending over Ten Nanometres Mediate Charge Transport in High‐Mobility Organic Crystals

Giannini

Ziogos

Carof

et al. 2020

Advcd Theory and Sims

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Progress in the design of high‐mobility organic semiconductors has been hampered by an incomplete fundamental understanding of the elusive charge carrier dynamics mediating electrical current in these materials. To address this problem, a novel fully atomistic non‐adiabatic molecular dynamics approach termed fragment orbital‐based surface hopping (FOB‐SH) that propagates the electron‐nuclear motion has been further improved and, for the first time, used to calculate the full 2D charge mobility tensor for the conductive planes of six structurally well characterized organic single crystals, in good agreement with available experimental data. The nature of the charge carrier in these materials is best described as a flickering polaron constantly changing shape and extensions under the influence of thermal disorder. Thermal intra‐band excitations from modestly delocalized band edge states (up to 5 nm or 10–20 molecules) to highly delocalized tail states (up to 10 nm or 40–60 molecules in the most conductive materials) give rise to short, ≈ 10 fs‐long bursts of the charge carrier wavefunction that drives the spatial displacement of the polaron, resulting in carrier diffusion and mobility. This study implies that key to the design of high‐mobility materials is a high density of strongly delocalized and thermally accessible tail states.

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j \neq a

c_{j} \to c_{j} \exp false(- normalΔ t / τ_{j a} false)

.…”

Section: Methodsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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Flickering Polarons Extending over Ten Nanometres Mediate Charge Transport in High‐Mobility Organic Crystals

Giannini

Ziogos

Carof

et al. 2020

Advcd Theory and Sims

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“…Using Marcus theory in this manner is similar to other recent high throughput methods which have evaluated structures using these types of properties. 11 As an assessment of its predictive power against a more complete description of charge transport, we carried out comparisons of Marcus theory against mobilities from non-adiabatic molecular dynamics [36][37][38][39][40][41] (see Table S2 and Fig. S4, ESI † for details) for a series of functionalised tetracenes.…”

Section: Electron Mobility Calculationsmentioning

confidence: 99%

Evolutionary chemical space exploration for functional materials: computational organic semiconductor discovery

2020

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Computational methods, including crystal structure and property prediction, have the potential to accelerate the materials discovery process by enabling structure prediction and screening of possible molecular building blocks prior to their synthesis. However, the discovery of new functional molecular materials is still limited by the need to identify promising molecules from a vast chemical space. We describe an evolutionary method which explores a user specified region of chemical space to identify promising molecules, which are subsequently evaluated using crystal structure prediction. We demonstrate the methods for the exploration of aza-substituted pentacenes with the aim of finding small molecule organic semiconductors with high charge carrier mobilities, where the space of possible substitution patterns is too large to exhaustively search using a high throughput approach. The method efficiently explores this large space, typically requiring calculations on only $1% of molecules during a search. The results reveal two promising structural motifs: aza-substituted naphtho[1,2-a]anthracenes with reorganisation energies as low as pentacene and a series of pyridazine-based molecules having both low reorganisation energies and high electron affinities. † Electronic supplementary information (ESI) available: Full details of computational methods, tting of molecular to solid-state electron affinities, ESF maps of all molecules, low energy predicted crystal structures and calculated properties. See

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“…Using Marcus theory in this manner is similar to other recent high throughput methods which have evaluated structures using these types of properties. 11 As an assessment of its predictive power against a more complete description of charge transport, we carried out comparisons of Marcus theory against mobilities from nonadiabatic molecular dynamics [36][37][38][39][40][41] (see Table S2 and Figure S4, ESI † for details) for a series of functionalised tetracenes. 41 These results indicate a good correlation for the majority of structures across the range of mobilities, but occasional outliers where Marcus theory predictions are poor.…”

Section: Electron Mobility Calculationsmentioning

confidence: 99%

Evolutionary Chemical Space Exploration for Functional Materials: Computational Organic Semiconductor Discovery

Cheng¹,

Campbell²,

Day

2020

Preprint

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Computational methods, including crystal structure and property prediction, have the potential to accelerate the materials discovery process by enabling structure prediction and screening of possible molecular building blocks prior to their synthesis. However, the discovery of new functional molecular materials is still limited by the need to identify promising molecules from a vast chemical space. We describe an evolutionary method which explores a user specified region of chemical space to identify promising molecules, which are subsequently evaluated using crystal structure prediction. We demonstrate the methods for the exploration of aza-substituted pentacenes with the aim of finding small molecule organic semiconductors with high charge carrier mobility, where the space of possible substitution patterns is too large to exhaustively search using a high throughput approach. The method efficiently explores this large space, typically requiring calculations on only ca.1% of molecules during a search. The results reveal two promising structural motifs: aza-substituted naphtho[1,2-a]anthracenes with reorganisation energies as low as pentacene and a series of pyridazine-based molecules having both low reorganisation energies and high electron affinities.

show abstract

How to calculate charge mobility in molecular materials from surface hopping non-adiabatic molecular dynamics – beyond the hopping/band paradigm

Cited by 39 publications

References 98 publications

Flickering Polarons Extending over Ten Nanometres Mediate Charge Transport in High‐Mobility Organic Crystals

Flickering Polarons Extending over Ten Nanometres Mediate Charge Transport in High‐Mobility Organic Crystals

Evolutionary chemical space exploration for functional materials: computational organic semiconductor discovery

Evolutionary Chemical Space Exploration for Functional Materials: Computational Organic Semiconductor Discovery

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