Nonlocal Electron–Phonon Coupling in Prototypical Molecular Semiconductors from First Principles
31 May 2018-Journal of Chemical Theory and Computation (American Chemical Society)-Vol. 14, Iss: 7, pp 3752-3762
TL;DR: This work compute the nonlocal electron-phonon coupling for the prototypical molecular semiconductors rubrene and tetracene using the phonon modes obtained from ab initio methods, and proposes a convenient decomposition of the delocalized lattice modes into molecular-based modes.
Abstract: A substantial amount of evidence indicates a relevant role played by the nonlocal electron–phonon couplings in the mechanism of charge transport in organic semiconductors. In this work, we compute the nonlocal electron–phonon coupling for the prototypical molecular semiconductors rubrene and tetracene using the phonon modes obtained from ab initio methods. We do not make the rigid molecular approximation allowing a mixing of intra- and intermolecular modes, and we use a supercell approach to sample the momentum space. Indeed, we find that some low-frequency intramolecular modes are mixed with the rigid-molecule translations and rotations in the modes with the strongest electron–phonon coupling. To rationalize the results we propose a convenient decomposition of the delocalized lattice modes into molecular-based modes.
Citations
More filters
TL;DR: In this paper, the authors describe a practical and flexible procedure to compute the charge carrier mobility in the transient localization regime, which can be transparently linked with the results of electronic structure calculations and can be used to extract the charge mobility at no additional cost.
Abstract: We describe a practical and flexible procedure to compute the charge carrier mobility in the transient localization regime. The method is straightforward to implement and computationally very inexpensive. We highlight the practical steps and provide sample computer codes. To demonstrate the flexibility of the method and generalize the theory, the correlation between the fluctuations of the transfer integrals is assessed. The method can be transparently linked with the results of electronic structure calculations and can therefore be used to extract the charge mobility at no additional cost.
42 citations
40 citations
TL;DR: In this article, the authors describe a methodology for the fast evaluation of the dynamic electronic disorder for molecular semiconductors from their crystalline structure, which is accelerated by using the Cartesian gradient of transfer integral and approximate phonons evaluated within the rigid body approximation.
Abstract: One of the key factors limiting the charge mobility of molecular semiconductors is the fluctuation of transfer integrals, also known as dynamic disorder. This is a manifestation of the nonlocal electron–phonon coupling, a property that is computationally expensive to evaluate and, so far, prevented the study of this property on large datasets of molecules. In this article, we describe a methodology for the fast evaluation of the dynamic electronic disorder for molecular semiconductors from their crystalline structure. The computation is accelerated by (i) the evaluation of the Cartesian gradient of transfer integral and (ii) the use of approximate phonons evaluated within the rigid body approximation. The quality of the approximations is checked against less-approximated alternatives. This method is used to study a range of molecular crystals, and some general trends on the behavior of the nonlocal electron–phonon coupling are discussed. A strategy to find the optimal relative position between interacting...
34 citations
TL;DR: The charge-carrier transport in thin-film organic semiconductors is strongly related to the molecular structure and the solid-state packing, which in turn are dependent on materials processing and devi... as mentioned in this paper.
Abstract: Charge-carrier transport in thin-film organic semiconductors is strongly related to the molecular structure and the solid-state packing, which in turn are dependent on materials processing and devi...
33 citations
TL;DR: The range of quantum dynamics approaches used to model the charge carrier dynamics stressing the strong and weak points of each method are considered on the basis of the available computational results.
Abstract: Computing the charge mobility of molecular semiconductors requires a balanced set of approximations covering both the electronic structure of the Hamiltonian parameters and the modeling of the charge dynamics. For problems of such complexity, it is hard to make progress without independently validating each layer of approximation. In this perspective, we survey how all terms of the model Hamiltonian can be computed and validated by independent experiments and discuss whether some common approximations made to build the model Hamiltonian are valid. We then consider the range of quantum dynamics approaches used to model the charge carrier dynamics stressing the strong and weak points of each method on the basis of the available computational results. Finally, we discuss non-trivial aspects and novel opportunities related to the comparison of theoretical predictions with recent experimental data.
30 citations
References
More filters
TL;DR: The revised DFT-D method is proposed as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.
Abstract: The method of dispersion correction as an add-on to standard Kohn-Sham density functional theory (DFT-D) has been refined regarding higher accuracy, broader range of applicability, and less empiricism. The main new ingredients are atom-pairwise specific dispersion coefficients and cutoff radii that are both computed from first principles. The coefficients for new eighth-order dispersion terms are computed using established recursion relations. System (geometry) dependent information is used for the first time in a DFT-D type approach by employing the new concept of fractional coordination numbers (CN). They are used to interpolate between dispersion coefficients of atoms in different chemical environments. The method only requires adjustment of two global parameters for each density functional, is asymptotically exact for a gas of weakly interacting neutral atoms, and easily allows the computation of atomic forces. Three-body nonadditivity terms are considered. The method has been assessed on standard benchmark sets for inter- and intramolecular noncovalent interactions with a particular emphasis on a consistent description of light and heavy element systems. The mean absolute deviations for the S22 benchmark set of noncovalent interactions for 11 standard density functionals decrease by 15%-40% compared to the previous (already accurate) DFT-D version. Spectacular improvements are found for a tripeptide-folding model and all tested metallic systems. The rectification of the long-range behavior and the use of more accurate C(6) coefficients also lead to a much better description of large (infinite) systems as shown for graphene sheets and the adsorption of benzene on an Ag(111) surface. For graphene it is found that the inclusion of three-body terms substantially (by about 10%) weakens the interlayer binding. We propose the revised DFT-D method as a general tool for the computation of the dispersion energy in molecules and solids of any kind with DFT and related (low-cost) electronic structure methods for large systems.
32,589 citations
University of Udine1, International School for Advanced Studies2, National Research Council3, Massachusetts Institute of Technology4, University of Paris5, Princeton University6, University of Minnesota7, ParisTech8, University of Milan9, International Centre for Theoretical Physics10, University of Paderborn11, ETH Zurich12, École Polytechnique Fédérale de Lausanne13
TL;DR: QUANTUM ESPRESSO as discussed by the authors is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave).
Abstract: QUANTUM ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). The acronym ESPRESSO stands for opEn Source Package for Research in Electronic Structure, Simulation, and Optimization. It is freely available to researchers around the world under the terms of the GNU General Public License. QUANTUM ESPRESSO builds upon newly-restructured electronic-structure codes that have been developed and tested by some of the original authors of novel electronic-structure algorithms and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency are still its main focus, with special attention paid to massively parallel architectures, and a great effort being devoted to user friendliness. QUANTUM ESPRESSO is evolving towards a distribution of independent and interoperable codes in the spirit of an open-source project, where researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.
19,985 citations
TL;DR: It is shown by an extensive benchmark on molecular energy data that the mathematical form of the damping function in DFT‐D methods has only a minor impact on the quality of the results and BJ‐damping seems to provide a physically correct short‐range behavior of correlation/dispersion even with unmodified standard functionals.
Abstract: It is shown by an extensive benchmark on molecular energy data that the mathematical form of the damping function in DFT-D methods has only a minor impact on the quality of the results. For 12 different functionals, a standard "zero-damping" formula and rational damping to finite values for small interatomic distances according to Becke and Johnson (BJ-damping) has been tested. The same (DFT-D3) scheme for the computation of the dispersion coefficients is used. The BJ-damping requires one fit parameter more for each functional (three instead of two) but has the advantage of avoiding repulsive interatomic forces at shorter distances. With BJ-damping better results for nonbonded distances and more clear effects of intramolecular dispersion in four representative molecular structures are found. For the noncovalently-bonded structures in the S22 set, both schemes lead to very similar intermolecular distances. For noncovalent interaction energies BJ-damping performs slightly better but both variants can be recommended in general. The exception to this is Hartree-Fock that can be recommended only in the BJ-variant and which is then close to the accuracy of corrected GGAs for non-covalent interactions. According to the thermodynamic benchmarks BJ-damping is more accurate especially for medium-range electron correlation problems and only small and practically insignificant double-counting effects are observed. It seems to provide a physically correct short-range behavior of correlation/dispersion even with unmodified standard functionals. In any case, the differences between the two methods are much smaller than the overall dispersion effect and often also smaller than the influence of the underlying density functional.
14,151 citations
TL;DR: Quantum ESPRESSO as discussed by the authors is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave).
Abstract: Quantum ESPRESSO is an integrated suite of computer codes for electronic-structure calculations and materials modeling, based on density-functional theory, plane waves, and pseudopotentials (norm-conserving, ultrasoft, and projector-augmented wave). Quantum ESPRESSO stands for "opEn Source Package for Research in Electronic Structure, Simulation, and Optimization". It is freely available to researchers around the world under the terms of the GNU General Public License. Quantum ESPRESSO builds upon newly-restructured electronic-structure codes that have been developed and tested by some of the original authors of novel electronic-structure algorithms and applied in the last twenty years by some of the leading materials modeling groups worldwide. Innovation and efficiency are still its main focus, with special attention paid to massively-parallel architectures, and a great effort being devoted to user friendliness. Quantum ESPRESSO is evolving towards a distribution of independent and inter-operable codes in the spirit of an open-source project, where researchers active in the field of electronic-structure calculations are encouraged to participate in the project by contributing their own codes or by implementing their own ideas into existing codes.
13,052 citations
TL;DR: Electronic Coupling in Oligoacene Derivatives: Factors Influencing Charge Mobility, and the Energy-Splitting-in-Dimer Method 3.1.
Abstract: 2.2. Materials 929 2.3. Factors Influencing Charge Mobility 931 2.3.1. Molecular Packing 931 2.3.2. Disorder 932 2.3.3. Temperature 933 2.3.4. Electric Field 934 2.3.5. Impurities 934 2.3.6. Pressure 934 2.3.7. Charge-Carrier Density 934 2.3.8. Size/molecular Weight 935 3. The Charge-Transport Parameters 935 3.1. Electronic Coupling 936 3.1.1. The Energy-Splitting-in-Dimer Method 936 3.1.2. The Orthogonality Issue 937 3.1.3. Impact of the Site Energy 937 3.1.4. Electronic Coupling in Oligoacene Derivatives 938
3,635 citations