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1. ALATDYN: A set of Anharmonic LATtice DYNamics codes to compute thermodynamic and thermal transport properties of crystalline solids

   https://doi.org/10.1016/j.cpc.2025.109575  

   Esfarjani, Keivan; Stokes, Harold; Nayeb_Sadeghi, Safoura; Liang, Yuan; Timalsina, Bikash; Meng, Han; Shiomi, Junichiro; Liao, Bolin; Sun, Ruoshi (July 2025, Computer Physics Communications)

   We introduce a lattice dynamics package which calculates elastic, thermodynamic and thermal transport properties of crystalline materials from data on their force and potential energy as a function of atomic positions. The data can come from density functional theory (DFT) calculations or classical molecular dynamics runs performed in a supercell. First, the model potential parameters, which are anharmonic force constants are extracted from the latter runs. Then, once the anharmonic model is defined, thermal conductivity and equilibrium properties at finite temperatures can be computed using lattice dynamics, Boltzmann transport theories, and a variational principle respectively. In addition, the software calculates the mechanical properties such as elastic tensor, Gruneisen parameters and the thermal expansion coefficient within the quasi-harmonic approximation (QHA). Phonons, elastic constants and thermodynamic properties results applied to the germanium crystal will be illustrated. Using the force constants as a force field, one may also perform molecular dynamics (MD) simulations in order to investigate the combined effects of anharmonicity and defect scattering beyond perturbation theory. 

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2. Tying Together Multiscale Calculations for Charge Transport in P3HT: Structural Descriptors, Morphology, and Tie-Chains

   https://doi.org/10.3390/polym10121358  

   Miller, Evan; Jones, Matthew; Jankowski, Eric (December 2018, Polymers)

   Evaluating new, promising organic molecules to make next-generation organic optoelectronic devices necessitates the evaluation of charge carrier transport performance through the semi-conducting medium. In this work, we utilize quantum chemical calculations (QCC) and kinetic Monte Carlo (KMC) simulations to predict the zero-field hole mobilities of ∼100 morphologies of the benchmark polymer poly(3-hexylthiophene), with varying simulation volume, structural order, and chain-length polydispersity. Morphologies with monodisperse chains were generated previously using an optimized molecular dynamics force-field and represent a spectrum of nanostructured order. We discover that a combined consideration of backbone clustering and system-wide disorder arising from side-chain conformations are correlated with hole mobility. Furthermore, we show that strongly interconnected thiophene backbones are required for efficient charge transport. This definitively shows the role “tie-chains” play in enabling mobile charges in P3HT. By marrying QCC and KMC over multiple length- and time-scales, we demonstrate that it is now possible to routinely probe the relationship between molecular nanostructure and device performance. 

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3. Temperature-dependent stress–strain behavior of amorphous and crystalline P3HT

   https://doi.org/10.1039/d4tc03618b  

   Fagbohungbe, Kehinde H; Callaway, Connor P; Risko, Chad (December 2024, Journal of Materials Chemistry C)

   Atomistic molecular dynamics (MD) simulations of ordered and disordered P3HT at varying temperatures reveal distinct thermomechanical behavior in the amorphous and crystalline material domains. 

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4. Charge-transfer-to-solvent states provide a sensitive spectroscopic probe of the local solvent structure around anions

   https://doi.org/10.1080/00268976.2022.2148582  

   Sarangi, Ronit; Nanda, Kaushik D.; Krylov, Anna I. (November 2022, Molecular Physics)

   This computational study characterises charge-transfer-to-solvent (CTTS) states of aqueous thiocyanate anion using equation-of-motion coupled-cluster methods combined with electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) scheme. Equilibrium sampling was carried out using classical molecular dynamics (MD) with standard force-fields and QM/MM ab initio molecular dynamics (AIMD) using density functional theory. The two calculations yield significantly different local structure around solvated SCN− . Because of the diffuse character of CTTS states, they are very sensitive to the local structure of solvent around the solute and its dynamic fluctuations. Owing to this sensitivity, the spectra computed using MD and AIMD based snapshots differ considerably. This sensitivity suggests that the spectroscopy exploiting CTTS transitions can provide an experimental handle for assessing the quality of force-fields and density functionals. By combining CTTS-based spectroscopies with reliable theoretical modeling, detailed microscopic information of the solvent structure can be obtained. We present a robust computational protocol for modeling spectra of solvated anions and emphasise the use of an ab initio characterization of individual electronic transitions as CTTS or local excitations. 

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5. Optimization and Validation of Efficient Models for Predicting Polythiophene Self-Assembly

   https://doi.org/10.3390/polym10121305  

   Miller, Evan; Jones, Matthew; Henry, Michael; Chery, Paul; Miller, Kyle; Jankowski, Eric (December 2018, Polymers)

   We develop an optimized force-field for poly(3-hexylthiophene) (P3HT) and demonstrate its utility for predicting thermodynamic self-assembly. In particular, we consider short oligomer chains, model electrostatics and solvent implicitly, and coarsely model solvent evaporation. We quantify the performance of our model to determine what the optimal system sizes are for exploring self-assembly at combinations of state variables. We perform molecular dynamics simulations to predict the self-assembly of P3HT at ∼350 combinations of temperature and solvent quality. Our structural calculations predict that the highest degrees of order are obtained with good solvents just below the melting temperature. We find our model produces the most accurate structural predictions to date, as measured by agreement with grazing incident X-ray scattering experiments. 

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