Many mechanical, dynamical and structural properties of materials remain poorly understood for reasons independent of system-specific chemistry. Great advances in understanding these properties can be achieved through coarse-grained and multiscale simulations that are computationally efficient enough to access experimentally accessible spatiotemporal scales yet "chemically" realistic enough to capture the essential physics underlying the properties under study. My research aims to explain poorly-understood behaviors of polymeric, glassy, and granular systems through coarse-grained modeling and concomitant development of analytic theories. Generally I aim do basic research on topics that are of substantial practical interest. More details can be found on my CV.



People


The group in Spring 2022: Kai Nan, Joseph Dietz, Rob Hoy, Pedro Abritta and Kevin Interiano-Alberto

Current students: Kevin Interiano-Alberto, Katrianna Sarkar Duncan
Alumni: Kai Nan, Sebastian Rocks, Cory Brown, Joseph Dietz, Pedro Abritta, Caitlin Gish, Austin Griffith, Elvin Salcedo, Hong Nguyen, Christian Plaza-Rivera, Tyler Smith, Krystle Quinn, Arvind Srikanth

Contact Info

University of South Florida
Department of Physics, ISA 4209
Tampa, FL 33620-5700
Phone: 813-399-2976
Fax: 813-974-5813
email: rshoy at usf dot edu

News

Rob began a rotating-program-drector position with NSF's DMR-CMMT program and will be spending the next 1-2 years in Alexandria, VA!

Kai Nan defended his thesis "Void formation in model liquids, polymer glasses, and granular materials" on 9/6/23 and has tarted working in a permanent position at DigiM (Boston, MA). Congrats Kai!

Joseph Dietz defended his thesis "Coarse-grained Modeling Studies of Entangled Semiflexible Polymers: Melts, Glasses, and Granular Media" on 10/21/22 and has started working in a permanent position at Northrup Grumman Corp (Gaithersburg, MD). Congrats Joe!

Rob won the USF Physics Department's 2021 Jewell Award for Faculty Excellence!

Christian Plaza-Rivera was accepted into MIT's Materials Science Ph.D. program and will begin his studies there in September 2021. Congrats Christian!

We received a 3-year, $315K grant from NSF's DMR-CMMT program to support our "Stress Testing Theories of the Glass and Jamming Transitions Using Hyperellipsoids" project!


Codes, Scripts, and Configurations

hdMD: Efficient high-dimensional molecular dynamics for studies of the glass-jamming transition
This code is described in our 2022 paper in Physical Review E.

Equilibrated well-entangled semiflexible Kremer-Grest melts and the LAMMPS scripts used to prepare them
(as described in our 2022 paper in J. Chem. Phys.


Papers

Craze Extension Ratio of Semiflexible Polymer Glasses
K. Nan and R. S. Hoy
Macromolecules v. 56, 8369 (2023) (pdf)

Structure of jammed ellipse packings with a wide range of aspect ratios
S. Rocks and R. S. Hoy
Soft Matter v. 19, 5701 (2023) (pdf)

Ultraslow settling kinetics of frictional cohesive powders
K. Nan and R. S. Hoy
Physical Review Letters v. 130, 166102 (2023) (pdf)

Structure of saturated random-sequential-adsorption ellipse packings
P. Abritta and R. S. Hoy
Physical Review E v. 106, 056404 (2022) (pdf)

The Z1+ package: Shortest multiple disconnected path for the analysis of entanglements in macromolecular systems
M. Kröger, J. D. Dietz, R. S. Hoy and C. Luap
Computer Physics Communications v. 283, 108567 (2022) (pdf)

Unexpected Ductility in Semiflexible Polymer Glasses with Entanglement Length Equal to their Kuhn Length
J. D. Dietz, K. Nan and R. S. Hoy
Physical Review Letters v. 129, 127801 (2022) (pdf)

Efficient d-dimensional molecular dynamics simulations for studies of the glass-jamming transition
R. S. Hoy and K. A. Interiano-Alberto
Physical Review E v. 105, 055305 (2022) (pdf)

Validation and Refinement of Unified Analytic Model for Flexible and Semiflexible Polymer Melt Entanglement
J. D. Dietz, M. Kröger and R. S. Hoy
Macromolecules v. 55, 3613 (2022) (pdf)

Facile equilibration of well-entangled semiflexible bead-spring polymer melts
J. D. Dietz and R. S. Hoy
Journal of Chemical Physics v. 156, 014103 (2022) (pdf)

How does the character of glassy-polymeric cavitation depend on entanglement density and the local Poisson ratio?
K. Nan, P. Abritta and R. S. Hoy
Macromolecules v. 54, 7347 (2021) (pdf)

Thermodynamic stability of hard sphere crystals in dimensions 3 through 10
P. Charbonneau, C. M. Gish, R. S. Hoy and P. K. Morse
European Physical Journal E v. 44, 101 (2021) (pdf)

Does the Sastry transition control cavitation in simple liquids?
C. M. Gish, K. Nan and R. S. Hoy
Journal of Chemical Physics v. 153, 184504 (2020) (pdf)

Two-stage athermal solidification of semiflexible polymers and fibers
J. D. Dietz and R. S. Hoy
Soft Matter v. 16, 6206 (2020) (pdf)

Unified analytic expressions for the entanglement length, tube diameter, and plateau modulus of polymer melts
R. S. Hoy and M. Kröger
Physical Review Letters v. 124, 147801 (2020) (pdf)

Multiscale modeling of sub-entanglement-scale chain stretching and strain hardening in deformed polymeric glasses
W. Zou, S. Moghadam, R. S. Hoy and R. G. Larson
Macromolecules v. 52, 9428 (2019) (pdf)

Factors influencing thermal solidification of bent-core trimers
E. D. Salcedo, H. T. Nguyen and R. S. Hoy
Journal of Chemical Physics v. 151, 134501 (2019) (pdf)

Densest versus jammed packings of bent-core trimers
A. D. Griffith and R. S. Hoy
Physical Review E v. 100, 022903 (2019) (pdf)

Thermalization of plastic flow versus stationarity of thermomechanical equilibrium in SGR theory
R. S. Hoy
European Physical Journal E v. 42, 2 (2019) (pdf)

Densest versus jammed packings of two-dimensional bent-core trimers
A. D. Griffith and R. S. Hoy
Physical Review E v. 98, 042910 (2018) (pdf)

Effect of the ratio lK/p on glassy-polymeric shear deformation mechanisms
H. T. Nguyen and R. S. Hoy
Macromolecules v. 51, 4370 (2018) (pdf)

From sticky-hard-sphere to Lennard-Jones-type clusters
L. Trombach, R. S. Hoy, D. J. Wales and P. Schwerdtfeger
Physical Review E v. 97, 044309 (2018) (pdf)

Thermalized formulation of soft glassy rheology
R. S. Hoy
Physical Review E v. 96, 063001 (2017) (pdf) [associated C++ thermalized-SGR code]

Isostaticity and the solidification of semiflexible polymer melts
C. Plaza-Rivera, H. T. Nguyen and R. S. Hoy
Soft Matter v. 13, 7948 (2017) (pdf)

Jamming of semiflexible polymers
R. S. Hoy
Physical Review Letters v. 118, 068002 (2017) (pdf)

Entanglements in glassy polymer crazing: cross-links or tubes?
T. Ge, C. Tzoumanekas, S. Anogiannakis, R. S. Hoy and M. O. Robbins
Macromolecules v. 50, 459 (2017) (pdf)

Effect of chain stiffness and temperature on the dynamics and microstructure of crystallizable bead-spring polymer melts
H. T. Nguyen and R. S. Hoy
Physical Review E v. 94, 052502 (2016) (pdf)

Controlled fragmentation of multimaterial fibres and films via polymer cold-drawing
S. Shabahang, G. Tao, J. J. Kaufman, Y. Qiao, L. Wei. T. Bouchenot, A. P. Gordon, Y. Fink, Y. Bai, R. S. Hoy, and A. F. Abouraddy
Nature v. 534, 529 (2016) (pdf)

Effect of chain stiffness on the competition between crystallization and glass-formation in model unentangled polymers
H. T. Nguyen, T. B. Smith, R. S. Hoy and N. Ch. Karayiannis
Journal of Chemical Physics v. 143, 144901 (2015) (pdf)

Effect of temperature, strain rate, and particle size on the yield stresses and post-yield strain softening of PMMA and its composites
J. Jancar, R. S. Hoy, E. Jancarova and J. Zidek
Polymer v. 63, 196 (2015) (pdf)

Structure and dynamics of model colloidal clusters with short-range attractions
R. S. Hoy
Physical Review E, v. 91. 012303 (2015) (pdf)

Role of entanglements and bond scission in high strain-rate deformation of polymer gels
Y. R. Sliozberg, R. S. Hoy, R. A. Mrozek, J. L. Lenhardt and J. W. Andzelm
Polymer v. 55, 2543 (2014) (pdf)

Effect of particle size, temperature, and deformation rate on the plastic flow and strain hardening response of PMMA composites
J. Jancar, R. S. Hoy, A. J. Lesser, E. Jancarova and J. Zidek
Macromolecules v. 46, 9409 (2013) (pdf)

Particle-scale reversibility in athermal particulate media below jamming
C. F. Schreck, R. S. Hoy, M. D. Shattuck and C. S. O'Hern
Physical Review E, v. 88, 052205 (2013) (pdf)

Nonlinear mechanics of thermoreversibly associating dendrimer glasses
A. Srikanth, R. S. Hoy, B. C. Rinderspacher and J. W. Andzelm
Physical Review E, v. 88, 042607 (2013) (pdf)

Simple model for chain packing and crystallization of soft colloidal polymers
R. S. Hoy and N. Ch. Karayiannis
Physical Review E, v. 88, 012601 (2013) (pdf)

Minimal energy packings of nearly flexible polymers
R. S. Hoy, J. Harwayne-Gidansky and C. S. O'Hern
Journal of Chemical Physics, v. 138, 054905 (2013) (pdf)

Structure of finite sphere packings via exact enumeration: implications for colloidal crystal nucleation
R. S. Hoy, J. Harwayne-Gidansky, and C. S. O'Hern
Physical Review E, v. 85, 051403 (2012) (pdf)

Glassy dynamics of crystallite formation: the role of covalent bonds
R. S. Hoy and C. S. O'Hern
Soft Matter, v. 8, 1215 (2012) (pdf)

Why is understanding glassy polymer mechanics so difficult?
R. S. Hoy
J. Polym. Sci. Part B - Polym. Phys. v. 49, 979 (2011) (pdf)

End grafted polymer nanoparticles in a polymeric matrix: effect of coverage and curvature
J. Kalb. D. Dukes, S. K. Kumar, R. S. Hoy and G. S. Grest
Soft Matter, v. 7, 1418 (2011) (pdf)

Viscoplasticity and large-scale chain relaxation in glassy-polymeric strain hardening
R. S. Hoy and C. S. O'Hern
Physical Review E, v. 82, 041803 (2010) (pdf)

Minimal energy packings and collapse of sticky tangent hard-sphere polymers
R. S. Hoy and C. S. O'Hern
Physical Review Letters, v. 105, 068001 (2010) (pdf)

Strain hardening in bidisperse polymer glasses: separating the roles of chain orientation and interchain entanglement
R. S. Hoy and M. O. Robbins
Journal of Chemical Physics v. 131, 244901 (2009) (pdf)

Thermoreversible associating polymer networks: I. Interplay of thermodynamics, chemical kinetics, and polymer physics
R. S. Hoy and G. H. Fredrickson
Journal of Chemical Physics v. 131, 224902 (2009) (pdf)

Topological analysis of polymeric melts: chain-length effects and fast-converging estimators for entanglement length
R. S. Hoy, K. Foteinopoulou, and M. Kröger
Physical Review E v. 80, 031803 (2009) (pdf)

Scaling of the strain hardening modulus of glassy polymers with the flow stress
M. O. Robbins and R. S. Hoy
J. Polym. Sci. Part B - Polym. Phys. v. 47, 1406 (2009) (pdf)

Strain hardening of polymer glasses: entanglements, energetics and plasticity
R. S. Hoy and M. O. Robbins
Phys. Rev. E v. 77, 031801 (2008) (pdf)

Entanglements of an end-grafted polymer brush in a polymeric matrix
R. S. Hoy and G. S. Grest
Macromolecules v. 40, 8389 (2007) (pdf)

Strain hardening in polymer glasses: limitations of network models
R. S. Hoy and M. O. Robbins
Phys. Rev. Lett. v. 99, 117801 (2007) (pdf)

Strain hardening of polymer glasses: effect of entanglement density, temperature, and rate
R. S. Hoy and M. O. Robbins
J. Polym. Sci. Part B - Polym. Phys. v. 44, 3487 (2006) (pdf)

Effect of equilibration on primitive path analyses of entangled polymers
R. S. Hoy and M. O. Robbins
Phys. Rev. E v. 72, 061802 (2005) (pdf)

Fcc-bcc transition for Yukawa interactions by applied strain deformation
R. S. Hoy and M. O. Robbins
Phys. Rev. E v. 69, 056103 (2004) (pdf)