Younggak Shin

About

Ph.D. in Mechanical Engineering (Kyung Hee University, 2024), currently a Postdoctoral Researcher at Yonsei University. My research focuses on atomistic simulation of materials under extreme conditions — particularly tungsten-based alloys in fusion reactor environments.

I develop and deploy large-scale Molecular Dynamics codes capable of simulating billions of atoms to study radiation damage, defect evolution, and microstructural behaviour in nuclear materials. I am equally passionate about the high-performance computing infrastructure that makes such simulations possible: parallelised code design, MPI-IO optimisation, and scalable algorithms for national supercomputers.

Work Experience

Education

Awards

Research Projects

Code Development

PolyPal: Massive-Scale Parallel Atomistic Structure Generation

Project Manager & Core Developer · 2022 – Present

• Parallelised code for generating polycrystalline structures with billions of atoms for MD simulations.
• Designed a unique MPI-IO multi-file output format enabling fast reads in parallelised MD codes.
• Near-perfect scalability: 10-billion-atom structure generated in under 3 min on 6,400 cores.
• Supports grain size gradients, preferred crystallographic orientation, and solute atom mixing.

→ Published · Computer Physics Communications 308, 109458 (2025)

Code Development

VITMAS: Massive-Scale Parallel Molecular Dynamics Code

Project Manager & Core Developer · 2021 – Present

• Custom MD code for PKA cascade simulations; tested on systems containing 8 billion atoms.
• Developed time integration, Nosé-Hoover thermostat, interatomic force, and multi-PKA routines.
• Production runs utilising ~100,000 cores at KISTI's Nurion-5 national supercomputer.
• Manuscript currently in preparation for submission to a scientific journal.

Simulation Study · Code Development

Electron Temperature Model for Collision Cascade MD Simulations

Lead Researcher · 2021 – 2024

• Modified LAMMPS to implement an electron-temperature-dependent two-temperature model (2TM).
• Calculated electronic specific heat and electron-phonon coupling constants via ab initio methods.
• Achieved great improvement in thermal conductivity across wide range of temperature.
• Demonstrated that electron-temperature dependence significantly affects defect production in W.

→ Published · Nuclear Fusion 64(10), 106001 (2024)

Safety Assessment

Safety Assessment Code for Commercial Fission Reactor (CANDU)

Solo Developer · 2020 – 2023

• Developed safety assessment code for pressure tubes in CANDU reactors in collaboration with KAERI.
• Implemented Leak-Before-Break and single-flaw assessment modules, integrated into a unified program.
• Verified physics-based and probabilistic prediction functions via sensitivity analysis on key parameters.
• Authored extensive internal technical reports and manuals. Data classified under KAERI agreement.

Visiting Project

Real-Time Rendering in Digital Twin System of Smart Factory

DFKI Smart Factory · Kaiserslautern, Germany · 2018 & 2019

• Contributed to rendering code for real-time manufacturing processes integrated with Microsoft HoloLens.
• Bridged the physical factory system with a mixed-reality digital twin environment.

Personal Project

Pi-Cluster Build

• Built a 4-node Raspberry Pi 3 cluster configured with OpenMPI and Slurm job scheduler.
• Used as a personal sandbox environment for debugging and testing parallel codes.

Personal Project

Kerr-like Schwarzschild Black Hole Web Simulation

• Real-time WebGL ray-tracing of photon geodesics in Schwarzschild spacetime.
• Renders gravitational lensing, photon sphere, event horizon, and a Kerr-inspired accretion disk.
• Interactive observer controls: distance, inclination, and field of view.

→ Live Simulation · singularity.yshin.xyz

Personal Project

Hydrogen Orbital Visualisation

• Real-time WebGL rendering of the hydrogen probability density |ψ_nℓm|² as ~300,000 instanced 3-D spheres, drawn by rejection sampling from the analytic wavefunction.
• Supports every orbital up to n = 6 (s, p, d, f, g, h).
• Interactive quantum-number controls and angular-momentum rotation animation.

→ Live Visualiser · ovis.yshin.xyz

Publications

• 2026
  Improved Defect Analysis Based on Atomic Connectivity in Polycrystalline Materials

  Shin, Y., Moul, V., Kang, K., & Lee, B.

  Nanotechnology, 37, 195701

  doi:10.1088/1361-6528/ae645b
• 2025
  PolyPal: A Parallel Microscale Virtual Specimen Generator

  Shin, Y., Moul, V., Kang, K., & Lee, B.

  Computer Physics Communications, 308, 109458

  doi:10.1016/j.cpc.2024.109458
• 2024
  Temperature-dependent electron–phonon coupling changes the damage cascades in neutron-irradiation molecular dynamics simulation in W

  Shin, Y., Kang, K., & Lee, B.

  Nuclear Fusion, 64(10), 106001

  doi:10.1088/1741-4326/ad64e7
• 2023
  The Effects of Attractive Interaction on Viscosity in Undercooled Kob–Andersen Liquids

  Moul, V., Shin, Y., & Lee, B.

  Multiscale Science and Engineering, 5, 160-165

  doi:10.1007/s42493-024-00101-1
• 2021
  Reduced interstitial mobility through multicomponent alloying in bcc W

  Shin, Y., Kang, K., & Lee, B.

  Fusion Engineering and Design, 172, 112745

  doi:1.1016/j.fusengdes.2021.112745

International Conferences

• 2026
  Graph-Theoretical Approach for Defect Detection in Polycrystalline Atomic Specimen

  Shin, Y., Moul, V., Kang, K., & Lee, B.  ·  TMS Annual Meeting, San Diego
• 2025
  From Grains to Gigabytes: Generating Massive Virtual Specimens for Irradiation Damage Study Invited

  Shin, Y., Moul, V., Kang, K., & Lee, B.  ·  IAEA 7th International Workshop on Models and Data for Plasma-Material Interactions in Fusion Devices, Vienna
• 2025
  A Polycrystal Generator for Large Scale Atomistic Calculations

  Shin, Y., Moul, V., Kang, K., & Lee, B.  ·  TMS Specialty Congress, Anaheim
• 2024
  Implementation of Electron Temperature Model to W Damage Cascades Molecular Dynamics Simulation under Neutron Irradiation

  Shin, Y., Kang, K., & Lee, B.  ·  11th International Conference on MMM, Prague
• 2023
  Grain-boundary Effects on the Irradiated Damages in W-Re Alloys

  Yoo, S., Shin, Y., Oh, S., Park, H., Kim, Y., Yoo, A., Kwon, O., Kang, K., Lee, B.  ·  TMS Annual Meeting, San Diego
• 2022
  Parallel I/O Optimization for Micrometer-Scale Atomistic Calculations under Extreme Conditions

  Yoo, S., Oh, S., Shin, Y., Kwon, O., Kang, K., & Lee, B.  ·  APS April Meeting, New York
• 2022
  Reduced Interstitial Mobility in W Based Transition Metal Ternary Systems

  Shin, Y., Lee, B., & Kang, K.  ·  TMS Annual Meeting, Anaheim

Skills