Simulated STEM and HRTEM images of sheared β" precipitates

The simulated scanning transmission electron microscopy (STEM) and high-resolution transmission electron microscopy (HRTEM) data in this repository form the basis for the publication "". They are simulated using the MULTEM package under the multislice and frozen phonon approximations. The data is provided as HDF files readable through the open source Python package HyperSpy. Blind source separation results of a principal component analysis (PCA) of two through-thickness HRTEM fast-Fourier image stacks are also provided as png images (MULTEM0101_FFT_Power_spectrum_RPCA_GoDec_bss and MULTEM0120_FFT_Power_spectrum_RPCA_GoDec_bss). These results can be obtained by performing a PCA decomposition followed by a blind source separation (with two components) of the respective data in e.g. HyperSpy.

Each simulation is given the generic label "MULTEMxxxx" and is performed on a specific atomistic model of a beta'' precipitate (present in ternary Al-Mg-Si alloys at peak-hardness). The different models and simulations relate to specific shearing configurations of the precipitates, which has been modelled as a rigid translation of the precipitate structure on a certain plane in a certain direction. The rigid translations usually correspond to a combination of one of the slip systems in fcc aluminium (i.e. a relative shift of a <1/2 1/2 0> Burgers vector on a {111} slip plane), but in some cases a (001) slip plane is investigated instead. While the preciptiate itself is rigidly sheared, the surrounding matrix is relaxed using molecular dynamics to imitate the strain field surrounding these precipitate structures.

Information about the models themselves are accessible through the metadata of each file as well as provided in this repository (see below). The shear configuration of the models are as follows:

• MULTEM0101: Not sheared
• MULTEM0102: 1x[-1-10]/(001) - A
• MULTEM0103: 1x[-101]/(111) - A
• MULTEM0104: 2x[-1-10]/(001) - A
• MULTEM0105: 2x[-101]/(111) - A
• MULTEM0106: 3x[-1-10]/(001) - A
• MULTEM0107: 3x[-101]/(111) - A
• MULTEM0108: 5x[-1-10]/(001) - A
• MULTEM0109: 5x[-101]/(111) - A
• MULTEM0110: 10x[-1-10]/(001) - A
• MULTEM0111: 10x[-101]/(111) - A
• MULTEM0112: 1x[1-10]/(001) - A
• MULTEM0113: 1x[1-10]/(111) - A
• MULTEM0114: 2x[1-10]/(001) - A
• MULTEM0115: 2x[1-10]/(111) - A
• MULTEM0116: 3x[1-10]/(001) - A
• MULTEM0117: 3x[1-10]/(111) - A
• MULTEM0118: 5x[1-10]/(001) - A
• MULTEM0119: 5x[1-10]/(111) - A
• MULTEM0120: 10x[1-10]/(001) - A
• MULTEM0121: 10x[1-10]/(111) - A
• MULTEM0122: 10x[-1-10]/(001) - B
• MULTEM0123: 10x[1-10]/(001) - B
• MULTEM0124: 10x[1-10]/(111) - B
• MULTEM0125: 10x[-1-10]/(001) - C
• MULTEM0126: 10x[1-10]/(001) - C
• MULTEM0127: 10x[1-10]/(111) - C
• MULTEM0128: 10x[-1-10]/(001) - D
• MULTEM0129: 10x[1-10]/(001) - D
• MULTEM0130: 10x[1-10]/(111) - D

In this list, the trailing letter A, B, C, or D indicates whether the shearing is evenly distributed along the precipitate (A), concentrated in a single plane some distance below the specimen surface (B), concentrated in a narrow region some distance below the specimen surface (C), or if the first half of the precipitate is sheared one way while the last half is sheared the opposite way (D). The crystallographic directions in these labels are aligned with [100]||X, [010]||Y and [001]||Z, where X, Y, and Z are the horizontal, vertical, and out-of-plane specimen directions (beam travels along Z).

The simulations with the trailing "_s" label correspond to STEM simulations of a smaller and centered region of the precipitate. A final set of STEM simulations with the labels "UCx_*" corresponds to simulations where the shearing configuration is 1x[1-10]/(001) but where the shearing plane lies "x" unit cells below the specimen surface.

The models are named differently from the labels, as they are used in a few different simulations and with various parameters as well. Their filenames follow the naming convention of "POSCAR_relaxed_b<N>_i<i>_j<j>.mat", where N, i, and j correspond to the number of shearing events, the burgers vector ID and the shear plane ID, respectively. A Burgers vector IDs 1, 2, and 3 correspond to [-101], [-1-10], and [1-10] directions, respectively, while the shear plane IDs 0 and 1 correspond to the (001) and (111) planes, respectively.