123,421 research outputs found
Models and algorithms for the next generation of glass transition studies
Successful computer studies of glass-forming materials need to overcome both
the natural tendency to structural ordering and the dramatic increase of
relaxation times at low temperatures. We present a comprehensive analysis of
eleven glass-forming models to demonstrate that both challenges can be
efficiently tackled using carefully designed models of size polydisperse
supercooled liquids together with an efficient Monte Carlo algorithm where
translational particle displacements are complemented by swaps of particle
pairs. We study a broad range of size polydispersities, using both discrete and
continuous mixtures, and we systematically investigate the role of particle
softness, attractivity and non-additivity of the interactions. Each system is
characterized by its robustness against structural ordering and by the
efficiency of the swap Monte Carlo algorithm. We show that the combined
optimisation of the potential's softness, polydispersity and non-additivity
leads to novel computer models with excellent glass-forming ability. For such
models, we achieve over ten orders of magnitude gain in the equilibration
timescale using the swap Monte Carlo algorithm, thus paving the way to
computational studies of static and thermodynamic properties under experimental
conditions. In addition, we provide microscopic insights into the performance
of the swap algorithm which should help optimizing models and algorithms even
further.Comment: 22 pages, 15 fig
Influence of pH and sequence in peptide aggregation via molecular simulation
We employ a recently developed coarse-grained model for peptides and proteins
where the effect of pH is automatically included. We explore the effect of pH
in the aggregation process of the amyloidogenic peptide KTVIIE and two related
sequences, using three different pH environments. Simulations using large
systems (24 peptides chains per box) allow us to correctly account for the
formation of realistic peptide aggregates. We evaluate the thermodynamic and
kinetic implications of changes in sequence and pH upon peptide aggregation,
and we discuss how a minimalistic coarse-grained model can account for these
details.Comment: 21 pages, 4 figure
Fluctuation effects in ternary AB+A+B polymeric emulsions
We present a Monte Carlo approach to incorporating the effect of thermal
fluctuations in field theories of polymeric fluids. This method is applied to a
field-theoretic model of a ternary blend of AB diblock copolymers with A and B
homopolymers. We find a shift in the line of order-disorder transitions from
their mean-field values, as well as strong signatures of the existence of a
bicontinuous microemulsion phase in the vicinity of the mean-field Lifshitz
critical point. This is in qualitative agreement with a recent series of
experiments conducted with various three-dimensional realizations of this model
system. Further, we also compare our results and the performance of the
presently proposed simulation method to that of an alternative method involving
the integration of complex Langevin dynamical equations.Comment: minor changes, references adde
Deducing effective light transport parameters in optically thin systems
We present an extensive Monte Carlo study on light transport in optically
thin slabs, addressing both axial and transverse propagation. We completely
characterize the so-called ballistic-to-diffusive transition, notably in terms
of the spatial variance of the transmitted/reflected profile. We test the
validity of the prediction cast by diffusion theory, that the spatial variance
should grow independently of absorption and, to a first approximation, of the
sample thickness and refractive index contrast. Based on a large set of
simulated data, we build a freely available look-up table routine allowing
reliable and precise determination of the microscopic transport parameters
starting from robust observables which are independent of absolute intensity
measurements. We also present the Monte Carlo software package that was
developed for the purpose of this study
- …