**potname=**- Name of potential, no default.
**potpars=**- Parameters for potential
(1st one is pattern speed). See
*potential(5NEMO)*for some examples. **potfile=**- Any optional data file associated with potential.
**r=**- Radii to sample. Notice for most potentials r=0 results in NaN’s or divisions by zero and generally bad output. [0:2:0.1]
**p=**- Angles to sample (in degrees). If exactly two
angles are given, and
**niter**> 0, an iterative approach is used (similar to the one in*potq(1NEMO)*) and is generally more accurate. If One angle is given, an exact "rotation curve" along that (position) angle is give, else an average force is used to derive the "rotation curve". Default: 0. (meaning slit rotation curve along the X axis) **t=**- Time to test potential at, if relevant [0.0]
**omega=**- Use this instead of any returned pattern speed.
**format=**- Format used to print numbers [%g] **not used yet**
**niter=**- Maximum
number of iterations to find the forces from which the rotation curve is
derived. Only used if exactly two angles
**p**are given. Careful: at each iteration the sample step is halved, doubling the CPU requirements. [10] **eps=**- Relative accuracy that stops the iterations. [0.001]

potrot pfenniger84 r=0.1:10:0.1 p=0 > tab1 potrot pfenniger84 r=0.1:10:0.1 p=90 > tab2 potrot pfenniger84 r=0.1:10:0.1 p=0:90:2 > tab3 tabmath tab1,tab2,tab3 - %1,%3,%6,%9 all | tabplot - 1 2,3,4 line=1,1 color=2,3,4Here’s a comparison between various methods for the same Pfenniger potential, at a radius where the force along major and minor axis differs most:

potrot pfenniger84 r=4 p=0 4 -0.0403306 0.401649 potrot pfenniger84 r=4 p=90 4 -0.0277544 0.333193 potrot pfenniger84 r=4 p=0:90:10 4 -0.031413 0.354474 potrot pfenniger84 r=4 p=0:90:2 4 -0.0311816 0.353166 potrot pfenniger84 r=4 p=0,90 ### Warning [potrot]: Testing an iterative procedure: niter=10 eps=0.001000 4 0 0.352989 8 potrot pfenniger84 r=4 p=0,90 eps=0.0001 niter=20 4 0 0.352822 12

07-Feb-05V0.1 CreatedPJT