About

Dimitrios Maroudas is a Distinguished Professor and Department Head of Chemical and Biomolecular Engineering at UMass Amherst, with affiliations in Materials Science & Engineering, Chemistry, and Nanotechnology. He joined UMass Amherst in 2002, having previously served on the faculty at the University of California, Santa Barbara from 1994 to 2002. His research focuses on multi-scale modeling of complex systems, emphasizing theoretical and computational materials science and engineering. His group investigates surface morphological evolution, the design of carbon nanomaterials such as graphene and nanocomposites, plasma-surface interactions relevant to nuclear fusion and electronic materials, charge transport in photovoltaic devices, and the synthesis and doping of semiconductor quantum dots for optoelectronic applications. Maroudas's work aims to simulate materials processing and function, predict the structure and properties of electronic and structural materials, and optimize nanostructured materials for electronic and energy technologies. His research employs a broad spectrum of computational methods, from ab initio calculations to continuum modeling, with a focus on establishing links between atomistic and macroscopic scales to understand the formation, evolution, and behavior of nano/micro-structures during processing and device operation.

Research topics

• Materials science
• Atomic physics
• Thermodynamics
• Nuclear physics
• Metallurgy
• Mechanics
• Chemistry
• Physics
• Computational chemistry
• Composite material
• Geometry
• Statistical physics

Selected publications

• Thermodynamic framework for nanostructure pattern formation in thin epitaxial films grown on pit-patterned semiconductor substrates

  Journal of Applied Physics · 2026-01-05

  articleOpen accessSenior author

  We present a comprehensive study of nanostructure pattern formation on coherently strained epitaxial thin films grown on crystalline semiconductor substrates patterned with periodic arrays of inverted truncated pyramidal and conical pits. Using an experimentally validated three-dimensional kinetic model for surface morphological evolution, we investigate how pit geometry and surface free energy anisotropy govern the formation and spatial organization of self-assembled nanostructures such as quantum dots and nanorings. We analyze in detail the influence of the film’s anisotropic surface free energy per unit area on the morphological features of the resulting nanostructures on the epitaxial film surface. We find that while surface free energy anisotropy alters the detailed morphological features, creating faceted morphologies rather than rounded ones in the grown nanostructures, the overall pattern and number of the formed nanostructures remain unaffected. Furthermore, we propose a thermodynamic framework based on the average surface chemical potential of the initial film/substrate heteroepitaxial configuration, which enables predictive control over nanostructure patterns through rational design of pit geometry. Simulations across a broad range of pit design parameters for both inverted truncated pyramidal and inverted truncated conical pits reveal that the surface chemical potential serves as a reliable descriptor for predicting nanostructure pattern formation. Our findings provide new insights that offer a foundational basis for engineering semiconductor surface topographies that can guide next-generation nanofabrication strategies.

  PublisherOA PDFDOI

• Effects of Surface Crystallographic Orientation on the Surface Morphological Response of Plasma-Facing Tungsten

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Surface morphological response of plasma-facing tungsten: Effects of surface crystallographic orientation and prediction of fuzz onset

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Helium aggregation and surface morphology near grain boundaries in plasma-facing tungsten

  Journal of Applied Physics · 2024-06-17 · 4 citations

  articleOpen access

  We conduct molecular dynamics simulations of helium in tungsten to study the interaction of helium with grain boundaries. Model systems with grain boundary planes perpendicular to the surface and parallel to the surface are considered. The net attraction of mobile helium to the grain boundary results in a “depleted region” within approximately 3.5 nm of the grain boundary plane at low fluence, and once on the plane of the grain boundary, helium transport slows considerably. Helium retention is also strongly affected by the grain boundaries and their density: grain boundary planes approximately 6 nm beneath the plasma-facing surface and parallel to the surface tend to reduce the maximum bubble size due to the attraction of mobile clusters to the grain boundary plane, which lowers the concentration of helium near the surface (where it is being implanted); grain boundaries perpendicular to the surface tend to increase retention due to retention on the grain boundary plane. For grain boundaries parallel to the surface, the strong gettering effect of the grain boundaries on helium results in essentially no helium penetration through the grain boundary during the first 1.5 μs of plasma exposure at a flux of 1.6×1025 m−2s−1, corresponding to fluences on the order of 1020 m−2. Coarse-grained simulations capable of capturing the long-term dynamics of helium aggregation near grain boundaries would be required to determine whether these effects would have any measurable impact on phenomena, such as tungsten fuzz growth.

  PublisherOA PDFDOI

• Plasma Surface Interactions: Predicting the Performance and Impact of Dynamic PFC Surfaces

  2024-01-08

  reportOpen access1st authorCorresponding

  The objective of this project is to develop, and integrate, high-performance simulation tools capable of predicting plasma-facing component (PFC) operating lifetime and the impact of the evolving surface morphology of tungsten-based PFCs on plasma contamination, including the dynamic recycling of fuel species and tritium retention, in future magnetic fusion devices. Establishing a fundamental physical understanding and developing predictive capabilities of plasma-surface interactions (PSI) requires simultaneously addressing complex and diverse physics occurring over a wide range of length (Angstroms to meters) and time (femtoseconds to years) scales, as well as integrating extensive physical processes across the plasma–surface interface. This requires development of not only detailed physics models and computational strategies at each scale, but also algorithms and methods to couple them effectively in a way that can be robustly validated. Deploying these tools requires the continued development and coupling of leadership-scale computational codes to describe the boundary plasma and the evolving PFC surface, as well as a host of simulations that bridge disparate scales to address complex physical and computational issues at the plasma–surface interface in multi-component materials systems for magnetic fusion energy development beyond ITER. This project will enable discovery of the key physical phenomena controlling critical PFC performance issues, and the quantitative prediction of their impact on PFC performance during both steady-state and transient plasma conditions. Such phenomena include: (i) surface evolution in regions of either net erosion or net deposition; (ii) the impact of the evolving surface composition and roughness on the retention and recycling of hydrogenic fuel isotopes; (iii) the impact of dilute impurities on surface morphological evolution and plasma contamination; and (iv) the effects of high-energy neutron damage on surface properties that could influence helium/hydrogenic species retention and recycling. The outcome of this project will be a suite of coupled plasma and materials modeling tools, and a leadership class PFC simulator to predict PFC evolution and feedback to the boundary plasma both during steady-state plasma operation and transient events. Success in the proposed research tasks will enable the prediction of both plasma fueling and the sources of impurity contamination that impact core plasma performance, and will lay the foundation for understanding, designing, and developing the materials required to meet the performance objectives of future fusion reactors. Advanced capabilities for predictive modeling of plasma-facing component (PFC) surface morphological evolution and near-surface structural evolution are required for evaluation of tungsten (W) as a PFC in ITER’s divertor and improvement of its performance. Atomistically-informed, hierarchically developed and properly parameterized continuum-scale models that can efficiently access the spatiotemporal scales of PFC tungsten dynamical response enable such quantitative predictions of PFC structural and morphological evolution. Toward this end, the research conducted at UMass Amherst focused on the development of a materials property and defect interaction database that is required for constitutive modeling of the mechanical response of PFC tungsten and heat and mass transport in the near-surface region and on the surface of the PFC material, as well as the development and continuous upgrading of surface morphological evolution models which will improve significantly the predictive accuracy of our PFC tungsten evolution simulators. This effort is within the scale-bridging mission of the PSI-SciDAC center. Specific research tasks executed at UMass Amherst included: (1) Development of comprehensive databases for: (a) PFC tungsten mechanical, thermal, and transport properties (including elastic properties, mechanical strength, thermal conductivity, coefficient of thermal expansion, diffusion coefficients, and heats of transport); and (b) energetics of plasma-related defect interactions in the PFC near-surface region; (2) Incorporation of the above databases into constitutive models to determine the level of stress, as well as heat and species fluxes in PFC tungsten under plasma exposure conditions; (3) Developing and continuous upgrading of our hierarchical, atomistically-informed continuum-scale models of PFC surface evolution by incorporating additional physics modules (diffusion mechanisms, bubble dynamics) into the models; and (4) Computational implementation of the above databases, constitutive models, and upgraded surface dynamics in our simulators for predicting surface and near-surface dynamical response of PFC tungsten, from He retention to surface damaged (fuzz) layer growth as a function of fluence, under realistic plasma exposure conditions. The atomistic simulations involved in the database development employed state-of-the-art interatomic interaction potentials with excellent predictive capabilities. Our PSI-SciDAC kinetic Monte Carlo simulators, surface morphological evolution simulators, and the Xolotl PFC simulator are properly upgraded by integrating into their capabilities the above property database, constitutive information, and additional physics modules (from surface diffusion mechanisms to subsurface bubble dynamics).

  PublisherOA PDFDOI

• Effects of surface anisotropy on the surface morphological response of plasma-facing tungsten

  Acta Materialia · 2024-08-23 · 9 citations

  articleOpen accessSenior authorCorresponding
  PublisherOA PDFDOI

• Effects of Surface Anisotropy on the Surface Morphological Response of Plasma-Facing Tungsten

  SSRN Electronic Journal · 2024-01-01 · 2 citations

  preprintOpen accessSenior author
  PublisherDOI

• Focus on plasma-facing materials in nuclear fusion reactors

  Materials Research Express · 2024-04-01 · 7 citations

  articleOpen accessSenior authorCorresponding

  Abstract Fusion energy is a promising, safe, and reliable green energy solution to the increasing energy demand. However, there are several materials challenges that need to be overcome to increase the technical readiness to a level that enables a fusion pilot plant on the grid. This focus issue aims to identify and address a set of such key impediments for realizing deuterium-tritium (D–T) fusion power in a tokamak reactor and highlight the most recent progress on those research frontiers. The main emphasis of this collection is on materials development challenges resulting from helium irradiation, neutron-induced degradation, thermomechanical loading, and the corrosive environment faced by the divertor and first-wall materials, commonly known as plasma-facing components, and blanket systems for tokamak fusion reactors.

  PublisherOA PDFDOI

• Molecular-Dynamics Analysis of the Mechanical Behavior of Plasma-Facing Tungsten

  ACS Applied Materials & Interfaces · 2023-01-31 · 7 citations

  articleOpen accessSenior authorCorresponding

  We report a systematic computational analysis of the mechanical behavior of plasma-facing component (PFC) tungsten focusing on the impact of void and helium (He) bubble defects on the mechanical response beyond the elastic regime. Specifically, we explore the effects of porosity and He atomic fraction on the mechanical properties and structural response of PFC tungsten, at varying temperature and bubble size. We find that the Young modulus of defective tungsten undergoes substantial softening that follows an exponential scaling relation as a function of matrix porosity and He atomic content. Beyond the elastic regime, our high strain rate simulations reveal that the presence of nanoscale spherical defects (empty voids and He bubbles) reduces the yield strength of tungsten in a monotonically decreasing fashion, obeying an exponential scaling relation as a function of tungsten matrix porosity and He concentration. Our detailed analysis of the structural response of PFC tungsten near the yield point reveals that yielding is initiated by emission of dislocation loops from bubble/matrix interfaces, mainly 1/2⟨111⟩ shear loops, followed by gliding and growth of these loops and reactions to form ⟨100⟩ dislocations. Furthermore, dislocation gliding on the ⟨111⟩{211} twin systems nucleates 1/6⟨111⟩ twin regions in the tungsten matrix. These dynamical processes reduce the stress in the matrix substantially. Subsequent dislocation interactions and depletion of the twin phases via nucleation and propagation of detwinning partials lead the tungsten matrix to a next deformation stage characterized by stress increase during applied straining. Our structural analysis reveals that the depletion of twin boundaries (areal defects) is strongly impacted by the density of He bubbles at higher porosities. After the initial stress relief upon yielding, increase in the dislocation density in conjunction with decrease in the areal defect density facilitates the initiation of dislocation-driven deformation mechanisms in the PFC crystal.

  PublisherOA PDFDOI

• Helium bubble size effects on the surface morphological response of plasma-facing tungsten

  Materials Research Express · 2023-07-01 · 7 citations

  articleOpen accessSenior authorCorresponding

  Abstract We report a simulation study on the effects of helium (He) bubble size on the morphological evolution and pattern formation on the surface of tungsten used as a plasma-facing component (PFC) in nuclear fusion devices. We have carried out a systematic investigation based on self-consistent dynamical simulations of surface morphological evolution according to an atomistically-informed, 3D continuum-scale model that captures well the relevant length and time scales of surface nanostructure formation in PFC tungsten. The model accounts for PFC surface diffusion, driven by the biaxial compressive stress originating from the over-pressurized He bubbles in the near-surface region of PFC tungsten as a result of He plasma exposure, combined with the formation of self-interstitial atoms in tungsten that diffuse toward the PFC surface and the flux of surface adatoms generated as a result of surface vacancy-adatom pair formation upon He implantation; this transport of surface adatoms contributes to the anisotropic growth of surface nanostructural features due to the different rates of adatom diffusion along and across step edges of islands on the tungsten surface. Our detailed analysis reveals that varying the average He bubble size plays an important role in the PFC surface growth kinetics as well as the resulting surface topography. Specifically, we find that an increase in the He bubble size leads to a deceleration in the growth rate of the tungsten nanotendrils that emanate from the PFC surface. We also find that the separation distance between the resulting surface features increases with increasing He bubble size, as well as over time. This coarsening effect is a thermally activated process resulting in an accurate description of the temperature dependence of the average surface feature separation by an Arrhenius relation.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: Plasma-Surface Interactions in Hydrogen Plasma-Induced Transitions from Carbon Nanotubes to Diamond Nanostructures

  NSF · $305k · 2006–2009

Frequent coauthors

• Brian D. Wirth

  Oak Ridge National Laboratory

  76 shared

• M. Rauf Gungor

  Ankara Sosyal Bilimler Üniversitesi

  57 shared

• Dwaipayan Dasgupta

  University of Tennessee at Knoxville

  42 shared

• Eray S. Aydil

  New York University

  42 shared

• Mayur S. Valipa

  University of Massachusetts Amherst

  28 shared

• André R. Muniz

  Universidade Federal do Rio Grande do Sul

  28 shared

• Karl D. Hammond

  University of Missouri

  27 shared

• Ashwin Ramasubramaniam

  University of Massachusetts Amherst

  22 shared

Awards & honors

• Fellow, American Institute of Chemical Engineers (AIChE), 20…
• Fellow, American Association for the Advancement of Science…
• Faculty Exceptional Merit Award, UMass Amherst, 2012
• College of Engineering Outstanding Senior Faculty Award, UMa…
• Camille Dreyfus Teacher-Scholar Award, 1999