I joined the theory group at the Max Planck Institute for Polymer
Research as a postdoctoral fellow in February 2015.
My position is funded by the collaborative research center TRR 146:
Multiscale Simulation Methods for Soft Matter Systems. Within the TRR
146, I work on many-body effects and optimized
mapping schemes for systematic coarse-graining. My current research
focusses on the extension of existing coarse graining schemes to include
3-body nonbonded interactions and the implementation in the coarse
graining toolkit VOTCA-CSG.
I obtained my PhD at Johannes Gutenberg-University Mainz in the
Condensed Matter Theory Group group KOMET 331, supervised by Prof.
Friederike Schmid in 2015 in collaboration with the SCHOTT AG in Mainz.
In my PhD, I focussed on classical and ab initio molecular dynamics
simulations of silicate and borate glasses and melts.
During my studies, I received a
Diploma in Physics (Dipl.-Phys.) from Johannes Gutenberg-University in
Mainz (2010) and a B.Sc. with Honours from the University of Canterbury
in Christchurch, New Zealand in 2007.
2024
Predicting molecular ordering in deposited molecular films
C. Scherer, N. Kinaret, K.-H. Lin, M. N. Qaisrani, F. Post, F. May, D. Andrienko
Adv. Energy Mater.,
14,
2403124,
2024,
[doi]
[abstract]
Abstract Thin films of molecular materials are commonly employed in organic light-emitting diodes field-effect transistors and solar cells. The morphology of these organic films is shown to depend heavily on the processing used during manufacturing such as vapor co-deposition. However the prediction of processing-dependent morphologies has until now posed a significant challenge particularly in cases where self-assembly and ordering are involved. In this work a method is developed based on coarse-graining that is capable of predicting molecular ordering in vapor-deposited films of organic materials. The method is tested on an extensive database of novel and known organic semiconductors. A good agreement between the anisotropy of the refractive indices of the simulated and experimental vapor-deposited films suggests that the method is quantitative and can predict the molecular orientations in organic films at an atomistic resolution. The methodology can be readily utilized for screening materials for organic light-emitting diodes.
2022
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Benchmarking coarse-grained models of organic semiconductors via deep backmapping
M. Stieffenhofer, C. Scherer, F. May, T. Bereau, D. Andrienko
Frontiers in Chemistry,
10,
982757,
2022,
[doi]
[abstract]
The potential of mean force is an effective coarse-grained potential which is often approximated by pairwise potentials. While the approximated potential reproduces certain distributions of the reference all-atom model with remarkable accuracy important cross-correlations are typically not captured. In general the quality of coarse-grained models is evaluated at the coarse-grained resolution hindering the detection of important discrepancies between the all-atom and coarse-grained ensembles. In this work the quality of different coarse-grained models is assessed at the atomistic resolution deploying reverse-mapping strategies. In particular coarse-grained structures for Tris-Meta-Biphenyl-Triazine are reverse-mapped from two different sources: (1) All-atom configurations projected onto the coarse-grained resolution and (2) snapshots obtained by molecular dynamics simulations based on the coarse-grained force fields. To assess the quality of the coarse-grained models reverse-mapped structures of both sources are compared revealing significant discrepancies between the all-atom and the coarse-grained ensembles. Specifically the reintroduced details enable force computations based on the all-atom force field that yield a clear ranking for the quality of the different coarse-grained models.
2021
Ultra-Coarse-Graining of Homopolymers in Inhomogeneous Systems
F. Berressem, C. Scherer, D. Andrienko, A. Nikoubashman
J. Phys. Condens. Matter,
33,
254002,
2021,
[doi]
[abstract]
We develop coarse-grained (CG) models for simulating homopolymers in inhomogeneous systems focusing on polymer films and droplets. If the CG polymers interact solely through two-body potentials then the films and droplets either dissolve or collapse into small aggregates depending on whether the effective polymer–polymer interactions have been determined from reference simulations in the bulk or at infinite dilution. To address this shortcoming we include higher order interactions either through an additional three-body potential or a local density-dependent potential (LDP). We parameterize the two- and three-body potentials via force matching and the LDP through relative entropy minimization. While the CG models with three-body interactions fail at reproducing stable polymer films and droplets CG simulations with an LDP are able to do so. Minor quantitative differences between the reference and the CG simulations namely a slight broadening of interfaces accompanied by a smaller surface tension in the CG simulations can be attributed to the deformation of polymers near the interfaces which cannot be resolved in the CG representation where the polymers are mapped to spherical beads.
Computing Inelastic Neutron Scattering Spectra from Molecular Dynamics Trajectories
T. Harrelson, M. Dettmann, C. Scherer, D. Andrienko, A. Moule, R. Faller
Scientific Reports,
11,
7938,
2021,
[doi]
[abstract]
Inelastic neutron scattering (INS) provides a weighted density of phonon modes. Currently INS spectra can only be interpreted for perfectly crystalline materials because of high computational cost for electronic simulations. INS has the potential to provide detailed morphological information if sufficiently large volumes and appropriate structural variety are simulated. Here we propose a method that allows direct comparison between INS data with molecular dynamics simulations a simulation method that is frequently used to simulate semicrystalline/amorphous materials. We illustrate the technique by analyzing spectra of a well-studied conjugated polymer poly(3-hexylthiophene-25-diyl) (P3HT) and conclude that our technique provides improved volume and structural variety but that the classical force field requires improvement before the morphology can be accurately interpreted.
2020
Kernel-based machine learning for efficient simulations of molecular liquids
C. Scherer, R. Scheid, D. Andrienko, T. Bereau
J. Chem. Theory Comput.,
16,
3194-3204,
2020,
[doi]
[abstract]
Current machine learning (ML) models aimed at learning force fields are plagued by their high computational cost at every integration time step. We describe a number of practical and computationally-efficient strategies to parametrize traditional force fields for molecular liquids from ML: the particle decomposition ansatz to two- and three-body force fields the use of kernel-based ML models that incorporate physical symmetries the incorporation of switching functions close to the cutoff and the use of covariant meshing to boost the training set size. Results are presented for model molecular liquids: pairwise Lennard-Jones three-body Stillinger-Weber and bottom-up coarse-graining of water. Here covariant meshing proves to be an efficient strategy to learn canonically averaged instantaneous forces. We show that molecular dynamics simulations with tabulated two- and three-body ML potentials are computationally efficient and recover two- and three-body distribution functions. Many-body representations decomposition and kernel regression schemes are all implemented in the open-source software package VOTCA.
2018
Understanding three-body contributions to coarse-grained force-fields
C. Scherer, D. Andrienko
Phys. Chem. Chem. Phys.,
20,
22387-22394,
2018,
[doi]
[abstract]
Coarse-graining (CG) is a systematic reduction of the number of degrees of freedom (DOF) used to describe a system of interest. CG can be thought of as a projection on coarse-grained DOF and is therefore dependent on the functions used to represent the CG force field. In this work we show that naive extensions of the coarse-grained force-field can result in unphysical parametrizations of the CG potential energy surface (PES). This issue can be elevated by coarse-graining the two- and three-body forces separately which also helps to evaluate the importance of many-body interactions for a given system. The approach is illustrated on liquid water where three-body interactions are essential to reproduce the structural properties and liquid methanol where two-body interactions are sufficient to reproduce the main features of the atomistic system.
2016
Comparison of systematic coarse-graining strategies for soluble conjugated polymers
C. Scherer, D. Andrienko
Eur. Phys. J. Spec. Top.,
225,
1441-1461,
2016,
[doi]
[abstract]
We assess several systematic coarse-graining approaches by coarse-graining poly(3-hexylthiophene-25-diyl) (P3HT) a polymer showing $\pi$-stacking of the thiophene rings and lamellar ordering of the $\pi$-stacked structures. All coarse-grained force fields are ranked according to their ability of preserving the experimentally known crystalline molecular arrangement of P3HT. The coarse-grained force fields parametrized in the amorphous melt turned out to accurately reproduce the structural quantities of the melt as well as to preserve the lamellar ordering of the P3HT oligomers in $\pi$-stacks. However the exact crystal structure is not reproduced. The combination of Boltzmann inversion for bonded and iterative Boltzmann inversion with pressure correction for nonbonded degrees of freedom gives the best coarse-grained model.
