Vlasios Mavrantzas

Last Name

Mavrantzas

First Name

Vlasios

ORCID

0000-0003-3599-0676

Organisational unit

09472 - Tibbitt, Mark / Tibbitt, Mark

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Publications 1 - 10 of 65

Chameleon: A generalized, connectivity altering software for tackling properties of realistic polymer systems
Alexiadis, Orestis; Cheimarios, Nikolaos; Peristeras, Loukas D.; et al. (2019)
Wiley Interdisciplinary Reviews. Computational Molecular Science
Ultrafast rotational motions of supported nanoclusters probed by electron diffraction
Vasileiadis, Thomas; Skountzos, Emmanuel N.; Foster, Dawn; et al. (2019)
Nanoscale Horizons
In crystals, microscopic energy flow is governed by electronic and vibrational excitations. In nanoscale materials, however, translations and rotations of entire nanoparticles represent additional fundamental excitations. The observation of such motions is elusive as most ultrafast techniques are insensitive to motions of the phonons’ frame of reference. Here, we study heterostructures of size-selected Au nanoclusters with partial (111) orientation on few-layer graphite with femtosecond electron diffraction. We demonstrate that ultrafast, constrained rotations of nanoclusters, so-called librations, in photo-induced non-equilibrium conditions can be observed separately from vibrational structural dynamics. Molecular dynamics and electron diffraction simulations provide quantitative understanding on librations-induced deviations from the conventional temperature dependence of diffraction patterns. We find that nanocluster librations with a period of ∼20 picoseconds are triggered quasi-impulsively by graphene flexural motions. These ultrafast structural dynamics modulate the Au/C interface and hence are expected to play a key role in energy- and mass-transport at the nanoscale.
Size and Diffusivity of Polymer Rings in Linear Polymer Matrices: The Key Role of Threading Events
Tsalikis, Dimitrios G.; Mavrantzas, Vlasios (2020)
Macromolecules
Mobility and settling rate of agglomerates of polydisperse nanoparticles
Spyrogianni, Anastasia; Karadima, Katerina S.; Goudeli, Eirini; et al. (2018)
The Journal of Chemical Physics
Scaling Laws for the Conformation and Viscosity of Ring Polymers in the Crossover Region around Mefrom Detailed Molecular Dynamics Simulations
Tsalikis, Dimitrios G.; Alatas, Panagiotis V.; Peristeras, Loukas D.; et al. (2018)
ACS Macro Letters
High Polymer Mass Densities at the Mouths of Carbon Nanotubes (CNTs) Control the Diffusion of Small Molecules through CNT-Based Polymer Nanocomposite Membranes
Mermigkis, Panagiotis G.; Skountzos, Emmanuel N.; Mavrantzas, Vlasios (2019)
The Journal of Physical Chemistry B
Individual Contributions of Adsorbed and Free Chains to Microscopic Dynamics of Unentangled poly(ethylene Glycol)/Silica Nanocomposite Melts and the Important Role of End Groups: Theory and Simulation
Skountzos, Emmanuel N.; Tsalikis, Dimitrios G.; Stephanou, Pavlos S.; et al. (2021)
Macromolecules
Molecular dynamics simulations and Rouse theory suitably adapted for polymer chains adsorbed by one or both of their ends are combined to offer a quantitative description of the local structure and microscopic dynamics in attractive polymer nanocomposite melts using a poly(ethylene glycol) (PEG)/silica nanocomposite as a model system. Our work reveals that the adsorbed layer around the silica nanoparticle is far from being characterized as "glassy"or "immobilized"since adsorbed polymer segments in the form of tails and loops on silica exhibit appreciable mobility locally, which helps adsorbed chains to relax at short length scales, albeit rather slowly. The simulations also reveal significant differences in the structural and dynamic properties of the PEG/silica nanocomposite melts studied for different terminal groups (hydroxyl versus methoxy) of the PEG chains, originating from the different ways that polymer chains adsorb on the silica surface: hydroxyl-terminated PEG chains are adsorbed by their ends giving rise to a brush-like structure, whereas methoxy-terminated ones are adsorbed equally probably along their entire contour, thus resulting in better packing of adsorbed segments. Due to the dense interfacial layer that develops in both cases, the diffusive behavior of free chains is also affected (it slows down compared to that in the corresponding pure PEG melt), especially in the nanocomposite where PEG chains are terminated with hydroxyl groups. Direct comparison of simulation and theoretical predictions with previously reported experimental data in the literature for the dynamic structure factor [Glomann et al., Phys. Rev. Lett. 2013, 110, 178001] for the same systems under the same temperature and pressure conditions reveals excellent agreement.
Molecular dynamics simulation of the local concentration and structure in multicomponent aerosol nanoparticles under atmospheric conditions
Karadima, Katerina S.; Mavrantzas, Vlasios; Pandis, Spyros N. (2017)
Physical Chemistry Chemical Physics
Geometric Analysis of Clusters of Free Volume Accessible to Small Penetrants and Their Connectivity in Polymer Nanocomposites Containing Carbon Nanotubes
Mermigkis, Panagiotis G.; Mavrantzas, Vlasios (2020)
Macromolecules
Delaunay tessellation followed by Monte Carlo integration is employed in order to determine the clusters of sites where a hard-sphere penetrant of radius rp equal to a few Angstroms can reside in model carbon nanotube-atactic poly(methyl-methacrylate) (CNT-PMMA) nanocomposite microstructures and analyze their dependence on penetrant size and temperature. Starting configurations for the geometric analysis are generated by cooling down to lower temperatures the atomistic structures fully equilibrated at a higher temperature by means of a long molecular dynamics simulation and re-equilibrating. Because the tetrahedra formed in the process of the Delaunay tessellation are irregular in space, an analytical calculation of free volume is a tough problem; to overcome this, we resort to Monte Carlo integration. By accounting for the volume occupied by polymers and CNT atoms, we obtain estimates of the unoccupied volume as well as of the volume accessible to a spherical penetrant of a given radius within each tetrahedron. From this, we calculate next the distribution of the volume and size of the corresponding cavities and of their clusters. By identifying neighboring clusters of tetrahedra that are mutually accessible to a given penetrant using a connectivity algorithm very similar to that proposed by Greenfield and Theodorou [Macromolecules,1993,26, 5461–5472], we quantify the network of clusters formed and determine probable pathways for diffusion for the penetrant under study. © 2020 American Chemical Society.
Quantitative Prediction of the Structure and Viscosity of Aqueous Micellar Solutions of Ionic Surfactants: A Combined Approach Based on Coarse-Grained MARTINI Simulations Followed by Reverse-Mapped All-Atom Molecular Dynamics Simulations
Peroukidis, Stavros D.; Tsalikis, Dimitrios G.; Noro, Massimo G.; et al. (2020)
Journal of Chemical Theory and Computation

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Vlasios Mavrantzas

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