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8.1. HRTEM simulation
seto edited this page Mar 23, 2026
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Simulates high-resolution TEM lattice-fringe images. The primary mode of the 8. HRTEM/STEM simulator.
- Bloch-wave method: compute electron wave propagation through the crystal potential; obtain exit-wave amplitude and phase
- Lens function: apply objective-lens aberrations (Cs, defocus Δf)
- Partial coherence: account for finite source size (spatial coherence) and energy spread (temporal coherence)
- Image formation: compute intensity |ψ(r)|²
| Parameter | Description |
|---|---|
| Thickness | Specimen thickness (nm). HRTEM images are strongly thickness-dependent |
| Parameter | Description |
|---|---|
| Acc. Vol. | Accelerating voltage (kV). Relativistically corrected wavelength shown alongside |
| Defocus | Defocus value (nm). Scherzer defocus displayed as reference |
| Parameter | Description | Typical |
|---|---|---|
| Cs | Spherical aberration (mm) | 0.5–1.0 (conventional); < 0.01 (Cs-corrected) |
| Cc | Chromatic aberration (mm) | 1.0–2.0 |
| β | Illumination semiangle (mrad) | 0.1–1.0 |
| ΔE | Energy spread 1/e width (eV) | 0.5–2.0 |
Displayed in the lens-function tab:
- Sin[χ(u)]: phase contrast transfer function
- Es(u): spatial coherence envelope
- Ec(u): temporal coherence envelope
Scherzer defocus: Δf = −1.2 (Cs λ)^(1/2), the condition giving a broad negative PCTF band (dark contrast = atom positions).
Set aperture size (mrad) and position. Open aperture removes it. The number of Bloch waves considered depends on aperture conditions.
| Model | Description |
|---|---|
| Quasi-coherent (linear image) | Fast. Valid under the weak-phase approximation |
| TCC (Transmission Cross Coefficient) | More accurate; longer computation |
| Mode | Description |
|---|---|
| Single image | One image at current thickness and defocus |
| Serial image | Matrix of images over thickness × defocus ranges (Start / Step / Num) |