models:analytic
Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
models:analytic [2018/09/16 10:49] – ↷ Links adapted because of a move operation daniel | models:analytic [2019/02/23 09:52] (current) – daniel | ||
---|---|---|---|
Line 3: | Line 3: | ||
---- | ---- | ||
- | Analytic potentials | + | Analytic potentials |
- | There are some additional options | + | A well-known example |
- | ==== Global parameters | + | $$V(r)=4\varepsilon\left[\left(\frac{\sigma}{r}\right)^{12}-\left(\frac{\sigma}{r}\right)^{6}\right]$$ |
- | //potfit// supports global parameters, which can occur in different potentials. With this feature it is possible for any potential to " | + | {{ :analytic.png?300 }} |
- | To use them, you need a section called '' | + | |
- | The format for the parameters is the same as for normal parameters: '' | + | |
- | If you want to use a global parameter in a potential, use the name of the global parameter and add an exclamation mark. | + | |
- | <code potfit> | + | Using an analytic form for $V(r)$ |
- | #F 0 3 | + | |
- | #C Mg Zn | + | |
- | #I 0 0 0 | + | |
- | #E | + | |
- | + | ||
- | global 2 | + | |
- | glob1 1 0 2 | + | |
- | glob2 2 0 5 | + | |
- | + | ||
- | type lj | + | |
- | cutoff 8 | + | |
- | glob1! | + | |
- | glob2! | + | |
- | + | ||
- | type lj | + | |
- | cutoff 8 | + | |
- | glob2! | + | |
- | glob1! | + | |
- | </ | + | |
- | + | ||
- | ==== Smooth Cutoff | + | |
- | + | ||
- | The smooth cutoff function is very important | + | |
- | potential and its gradient vanish at the desired cutoff radius. | + | |
- | Therefore the potential is multiplied with a cutoff function | + | |
- | + | ||
- | $$V_{SC}(r)=\Psi\left(\frac{r-r_c}{h}\right)V(r)\qquad\text{where}\qquad\Psi(x)=\frac{x^4}{1+x^4}$$ | + | |
- | + | ||
- | To enable | + | |
- | + | ||
- | <code potfit> | + | |
- | type lj_sc | + | |
- | cutoff 7 | + | |
- | epsilon 0.1 0 1 | + | |
- | sigma 2.5 1 4 | + | |
- | h 1 0 2 | + | |
- | </ | + | |
- | + | ||
- | Potentials fitted with the '' | + | |
- | If you omit it, it will be kept fixed at a value of 1. | + | |
- | + | ||
- | ==== Implemented Potential Functions | + | |
- | + | ||
- | The currently implemented analytic potential functions can be found [[: | + | |
- | + | ||
- | ==== Adding New Potential Functions | + | |
- | + | ||
- | If you want to add other analytic potentials see [[: | + | |
+ | The analytic potential implementation in //potfit// has additional features which are only useful with this kind of interactions. They are described on the [[potfiles:: |
models/analytic.1537087786.txt.gz · Last modified: 2018/09/16 10:49 by daniel