Current
research topics
Past projects
- Nonequilibrium
statistical physics of driven disordered
solids
Amorphous metals, polymers, and oxide glasses find many applications in sustainable, energy saving devices. Improving their performance requires fundamental insight into the molecular level processes that control yield, flow, stability, resistance to wear, and dissipation. We use atomistic simulations of model glasses subject to mechanical and thermal excitation to obtain statistical measures of the local elastic and plastic properties in such disordered packings, and characterize their nonequilibrium response. This information is used to build coarser (mesoscopic or mean-field) descriptions with the goal of building a statistical theory of plastic flow that is systematically linked to processes at the atomic scale.
- Thermal
transport in nanostructures and amorphous
polymers
We study materials with unusually high or low thermal conductivity. Carbon nanotubes are among the best known 1D heat conductors, yet nanotube forests were found to be able to localize heat and function as thermionic devices. By contrast, the thermal conductivity of amorphous polymers is among the lowest of all materials, which limits their applications in electronic packaging, OLEDs or photovoltaics where heat must be removed quickly. We use direct molecular simulations and Boltzmann transport theory to compute thermal properties of materials, and to learn how we can tune it at will by engineering the molecular interactions.
- Polyelectrolyte
hydrogels for sensors and diodes
Growing interest in motion capture, soft robotics, and wearable medical technologies has stimulated increasing interest in electronic materials that are flexible, conductive and biocompatible. Polyelectrolyte gels are particularly interesting materials that can respond to a pressure gradient with an electrical potential. This so-called piezoionic effect can be used to builld touch-sensors. Layered structures can act as a diode, i.e. they rectify a ionic current. We study these phenomena on the molecular level using molecular dynamics simulations, which we use to test and improve continuum electrostatic descriptions that can be deployed more readily on the engineering scale.
Past projects
- Atomistic
properties flow defects in amorphous solids
- Correlation between structure and plasticity
in flowing glassy matter
Predicting plasticity with soft vibrational modes: From dislocations to glasses, Physical Review E 89,042304 (2014).
Understanding Plastic Deformation in Thermal Glasses from Single-Soft-Spot Dynamics, Physical Review X 4, 031014 (2014)
Identifying structural flow defects in amorphous solids, Phys. Rev. Lett. 114, 108001 (2015)
Structural relaxation in glassy polymers predicted by soft modes: A quantitative analysis, Soft Matter, 10, 8533-8541 (2014)
- Nature of plastic events in glassy solids
Time dependent elastic response to a local shear transformation in amorphous solids, Phys. Rev. E 89, 042302 (2014)
Plastic response and correlations in athermally sheared amorphous solids, Phys. Rev E 94, 032604 (2016)
- Linking atomic scale dynamics to mesoscopic
models
Spatiotemporal correlations between plastic events in the shear flow of athermal amorphous solids, The European Physical Journal E 37, 1-11 (2014)
- Effect
of inertia on the steady state shear rheology
of amorphous solids, Phys. Rev. Lett. 116,
058303 (2016)
- Correlation between structure and plasticity
in flowing glassy matter
- Polymer physics
- Nanostructured block
copolymers
Using
soft potentials for the simulation of block
copolymer morphologies, Macromolecular
Theory and Simulations 23, 401-409 (2014)
Molecular mechanisms of plastic deformation in sphere-forming thermoplastic elastomers, Macromolecules 48 (22), 8253 (2015)
Nonlinear Mechanics of Triblock Copolymer Elastomers: From Molecular Simulations to Network Models, ACS Macro Letters 6, 786 (2017)
- Semicrystalline polymers
Plastic Deformation Mechanisms of Semicrystalline and Amorphous Polymers, ACS Macro Lett. 4, 147150 (2015)
Correlation of structure and mechanical response in solid-like polymers, J. Phys.: Condens. Matter 27, 194131 (2015)
Role of the Intercrystalline Tie Chains Network in the Mechanical Response of Semicrystalline Polymers, Phys. Rev. Lett. 118, 217802 (2017)
Molecular dynamics simulations of monodisperse and bidisperse polymer melt crystallization (2016), J. Polymer Science Part B: Polymer Physics 54, 2318 (2016)
- Physical Aging and
Mechanical Rejuvenation
Recovery of polymer glasses from mechanical perturbation, Macromolecules 45, 2928-2935 (2012)
Relaxation times in deformed polymer glasses: a comparison between molecular simulations and two theories, J. Chem. Phys. 145, 064505 (2016).
- Nanostructured block
copolymers
- Biopolymers
- Coarse-grained models
for DNA
A
systematically coarse grained model for DNA,
and its predictions for persistence length,
stacking, twist, and chirality,
J. Chem. Phys. 132, 035105-035121 (2010)
- Protein force
spectroscopy
As simple as
possible but not simpler: exploring the limits
of validity of coarse-grained protein models
for simulated force spectroscopy.
PLOS Computational Biology 12(11): e1005211
Soft Vibrational Modes Predict Breaking Events during Force-Induced Protein Unfolding, Biophysical Journal 114, 562 (2018).
- Coarse-grained models
for DNA
- Interface
Phenomena
Dewetting
during Terahertz Vibrations of
Nanoparticles, Nano Letters 18, 773
(2018). - Materials
Science
- New computational
methods to study segregation phenomena in
alloys
Solute-defect interactions in Al-Mg alloys from di ffusive variational Gaussian calculations, Phys. Rev. B 90, 174102 (2014)
Solute segregation kinetics and dislocation de-pinning in a binary alloy, Phys. Rev. B 91, 224103 (2015)
- Development of the Phase
Field Crystal Method
Free energy functionals for efficient phase field crystal modeling of structural phase transformations, Phys. Rev. Lett. 105, 045702 (2010)
Defect stability in phase field crystal models: Stacking faults and partial dislocations, Phys. Rev. B 86, 224112 (2012)
Phase fi eld crystal modeling
as a uni fied atomistic approach to defect
dynamics, Physical Review B 89, 214117 (2014) - Development of QM/MM
approaches for ab-initio studies of impurities
at interfaces
A QM/MM approach for low-symmetry defects in metals, Computational Materials Science 118, 259 (2016) - Ab
initio modelling of solute segregation
energies to a general grain boundary, Acta
Materialia 132, 138 (2017)
- New computational
methods to study segregation phenomena in
alloys