HRTEM Simulation
Simulates high-resolution TEM lattice-fringe images. The primary mode of the 8. HRTEM/STEM simulator.
Calculation flow
- 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
Specimen parameters
| Parameter |
Description |
| Thickness |
Specimen thickness (nm). HRTEM images are strongly thickness-dependent |
Optical parameters
TEM conditions
| Parameter |
Description |
| Acc. Vol. |
Accelerating voltage (kV). Relativistically corrected wavelength shown alongside |
| Defocus |
Defocus value (nm). Scherzer defocus displayed as reference |
Intrinsic parameters
| 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 |
Phase Contrast Transfer Function (PCTF)
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).
Objective aperture
Set aperture size (mrad) and position. Open aperture removes it. The number of Bloch waves considered depends on aperture conditions.
Partial coherence models
| Model |
Description |
| Quasi-coherent (linear image) |
Fast. Valid under the weak-phase approximation |
| TCC (Transmission Cross Coefficient) |
More accurate; longer computation |
Simulation modes
| Mode |
Description |
| Single image |
One image at current thickness and defocus |
| Serial image |
Matrix of images over thickness × defocus ranges (Start / Step / Num) |
See also