For simple harmonic boundary conditions, a single potential with an exponent of 2 or 4 may be used to obtain a potential like that shown in figure 5. It may be desirable, however, to simulate a surface tension affect, where a small harmonic well around the sphere boundary is desired. To obtain such an effect, two potentials of the form shown above can be superimposed. By combining a potential with a negative force constant and an exponent of two with a potential with a positive force constant and a exponent of four and a slightly larger raidus, a potential such as that shown in figure 6 can be obtained.
Currently, the spheres must be centered around the initial center of mass
of the system. The force constant, radius, and exponents for each potential
are defined in the configuration file using the options sphericalBCk1
,
sphericalBCr1
, sphericalBCexp1
, sphericalBCk2
,
sphericalBCr2
, and sphericalBCexp2
. These parameters are
described in section 4.