1. Free download with instructions
A Brief Instruction to VEC
Hua Jiang
Free download with instructions
and examples at

2. The big picture d dI dI Phases inside inner sphere Phases between
Amplitudes
inside two spheres
Phases between
two spheres
Phase extension D d dI dI
structure

3. far from the Scherzer defocus
Deconvolution of a Single EM
far from the Scherzer defocus
Original image
Image of the final model
Image after Fourier recycling
Averaged image
Deconvoluted image

4. Original EM from Prof. N. Uyeda
Symmetry
averaging
ED from Prof N. Uyeda
Original EM from Prof. N. Uyeda
Two-Step Image Processing
Image
deconvolution
Phase
extension
Fourier
recycling
Search for defocus
Partial
structure
model
Complete

5. Getting started Format: Image file (8-bit gray-level bitmap)
HREM image (.bmp)
Format: Image file (8-bit gray-level bitmap)
Electron diffraction data (.dhk)
Format: ASCII file
Two modes are available to open this file
Lattice parameters of the crystal
Unit cell: a, b, c, , , 
Space group

6. Pre - processing
Fourier filtering
Symmetry averaging

7. Searching for focus value
Experimental estimation (rough value):
Minimum-contrast defocus:
Focusing steps
The rough defocus value for the image

8. Searching for focus value
a set of trial f around the rough defocus value
direct method by Sayre Equation:
figures of merit (FOM)
For Direct Methods, figures of merit are a measure of the quality of a given phase set. They characterize how well the phase set is satisfying the Sayre equation.

9. Image deconvolution Low-resolution structure restoration
The resolution of the deconvoluted image is limited
by the image resolution of the microscope.

10. Phase extension direct method by Sayre Equation: Program: SAPI
for solving conventional and commensurate modulated structures (superstructures).
Program: DIMS
for 1D-incommensurate structures
DIMS is based on the multidimensional direct methods

11. others
modeling:
Based on either a deconvoluted image or a resolution-enhanced image, a structure mode can be built.
simulation:
Dynamical ED and HREM simulation in VEC are available but still in a primary stage.
A special feature of the simulation in VEC is that it can handle one-dimensionally modulated incommensurate crystals.

12. More others working with four-dimension (4D) structure:
Commensurate modulated structure.
Incommensurate modulated structure.

13. What’s a Modulated Structure ?
T ¹ 0 (mod t) or MOD (T, t) ¹ 0
Incommensurate modulation Þ
incommensurate structures t T
T = 0 (mod t) or MOD (T, t) = 0
Commensurate modulation Þ
superstructures

14. An example:
Bi2(Sr0.9La0.1)2CoOy
JEOL-2010, resolution ~ 2 Å

15. Schematic diffraction pattern of an incommensurate modulated structureb* q

16. Applications VEC has been successfully applied to structure
determination of ten different crystals so far:
Two commensurate modulated structure.
Three incommensurate modulated structure.
Five other conventional crystals.
More ongoing cases….

17. Demo Now…
But, don’t trust DEMO so much 