Data related to: Fast low-temperature irradiation creep driven by athermal defect dynamics

Data set related to article "Fast low-temperature irradiation creep driven by athermal defect dynamics"

Simulation data

Molecular dynamics data

The molecular dynamics data is the output of simulations of single-crystal tungsten with periodic boundary conditions evolving under irradiation up to high dose (0.5 dpa). The simulations are performed under a constant externally applied stress, uniaxial to z-direction, and zero stress conditions otherwise. Simulations were performed for stresses of -1.0 GPa, -0.5 GPa, 0 GPa, 0.5 GPa, 1.0 GPa, 1.5 GPa, and 2.0 GPa. Each stress condition was simulated five times independently. Simulations were performed in LAMMPS (see below for the simulation script). Only every 100th frame in LAMMPS Dump format is uploaded here. A frame corresponds to a dose increment of approximately 0.0002 dpa, i.e. frame 1000 corresponds to a dose of approximately 0.2 dpa. The files are zipped. A finer resolution can be supplied upon request (up to every 5th frame).

The zip archive naming convention is as follows:

For example, archive "srim_neg1p0.zip" contains data of the 5 simulations for -1.0 GPa (='negative 1 point 0'), where snapshot "srim_neg1p0_2/srim_neg1p0_2.1300.dump" refers to independent simulation ID 2, frame 1300, i.e. at a dose of 0.26 dpa. 

"srim_pos0p5.zip" contains the 5 simulations for 0.5 GPa (='positive 0 point 5'), and so on.

Archive "logfiles.zip" contains the simulation output information, containing stresses and box dimensions for every cascade iteration of each simulation. These can be used to generate the box eigenstrains. The columns are defined as follows:

iteration number, dose (dpa), total potential energy (eV), pressure xx (bar), pressure yy (bar), pressure zz (bar), pressure xy (bar), pressure xz (bar), pressure yz (bar), simulation box width x (Å), simulation box width y (Å), simulation box width z (Å)

The files contain a few lines labelled with "# restart", which marks points at which the simulation was terminated and then continued.

Archive "md_eigenstrains.zip" contains the eigenstrain tensor components parallel and perpendicular to the uniaxial stress direction obtained directly from the MD simulations. The format is as follows:

For example, files "eigenpara_pos0p5_0.dat" and "eigenperp_pos0p5_0" contain the MD eigenstrains parallel and perpendicular to the uniaxial loading direction of simulation "eigenpara_pos0p5_0", respectively. The first column is the NRT dose (dpa), and the second column is the eigenstrain value at this dose. The perpendicular eigenstrain is the average of the eigenstrain components xx and yy.

Molecular dynamics script

The LAMMPS script for performing high-dose collision cascade simulations is available at:

 https://github.com/mb4512/ezcascades

The simulation input files required to replicate the molecular dynamics simulations of this work are supplied here. Archive "md_input_files.zip" contains simulation input files, specifying box dimensions, stress constraints, the interatomic potential, paths to simulation and scratch directories, and so on. For example, "srim_neg1p0_0.json" is the input file for the "srim_neg1p0_0" simulation.

The interatomic potential "W_MNB_JPCM17.eam.fs" used here is the embedded atom method potential for tungsten developed by Mason et al: 10.1088/1361-648X/aa9776, available at the NIST Interatomic Potentials Repository.

Surrogate model data

Archive "eigenstrain_models.zip" contains the MLE model parameters for the eigenstrain surrogate models. The format is as follows:

For example, files "eigenpara_neg0p5.log" and  "eigenperp_neg0p5.log" contain the cubic spline knot points for the MLE model of eigenstrains parallel and perpendicular to the uniaxial loading direction at -0.5 GPa, respectively. The file contains columns labelled as x, y, and sigma, which correspond to dose (dpa), eigenstrain mean, and eigenstrain standard deviation, respectively. The spline boundary conditions are f(x = 0) = 0, f''(x = 0) = 0, and f'(x_end) = 0, where x_end is the final dose value in the list. The model is extrapolated for higher doses: f(x > x_end) = f(x_end).

The log files also contain the covariance matrix of the eigenstrain mean values, from which model uncertainties can be derived.

Archive "doseprofile.zip" contains the irradiation dose profile as generated using SRIM data following the procedure described in the Supplemental Information. The content is as follows:

Files "vacgrid_x_8micro_HR.dat", "vacgrid_y_8micro_HR.dat" contain the x and y coordinates of the 2 dimensional grid, respectively. File "vacgrid_z_8micro_HR.dat" contains a list of dose values (in arbitrary units). The values are ordered consistently, that is, the n-th values of each file give the matching tuple (x, y, dose(x,y)).