Benzene molecule in a magnetic field¶
This tutorial will show you how to:
handle the effect of a magnetic field on a molecule using BAND
visualize the resulting vector field (magnetic current) as vectors, and as streamlines
Step 1: amsinput¶
Start AMSinput in a clean directory.
Step 2: Setup the system - benzene¶
Make a benzene molecule. One easy way is to search (
) for Benzene and select it.
Go to the Main panel for BAND, and turn of periodicity:
→ 
and turn on the magnetic field:
Step 3: Run the calculation¶
Now you can save and run the calculation.
Step 4a: Magnetic current: vectors¶
After the calculation finished, open the result file with AMSview:
Add a vector field:
You will not see any vectors yet. The reason is that the vectors are very small. If you move the mouse over the real field at the bottom right (the max-color field), you can notice the range in the help balloon.
The vectors in the Clamp range will be scaled to vectors in the 0 .. 1 range. To make our vectors visible, change the upper clamp value to a smaller number:
Now you should see your vector field similar to this:
If you wish you can play with the values in the control line. Please use the help balloons, the meaning of those values is not obvious!
Step 4b: Magnetic current: streamlines¶
Another way to visualize a vector field is to generate streamlines.
Conceptually, one defines seed points, and then a line is generated starting at each seed point, following the vectors. For visualization purposed, a tube is generated around the lines, and the width of the tube depends on the magnitude of the vectors.
There are many options, the most important is to select the seed points. Again, the help balloons are important, they describe in detail what the controls do.
The default is to use starting points randomly distributed in a sphere:
An alternative is to define a line, and generate the starting points linearly distributed along that line. You can activate controls for the line to position it as you want.
Finally you can use a grid in a plane as starting points for the streamlines. Npts is the number of grid lines per dimension, thus the number of streamlines will be the square of Npts if you are using a plane.
The StreamLines technique has some important Detail options. To get them, select the Show Details option from the StreamLines pull-down menu at the bottom. The help balloons give the details, especially the streamline radius and the scaling method (flux or norm) are important.
Now try for yourself, make some nice looking picture… the following was made combining several techniques from above.
