potfiles:format0
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potfiles:format0 [2018/09/23 10:42] – daniel | potfiles:format0 [2021/03/29 21:08] (current) – daniel | ||
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~~NOTOC~~ | ~~NOTOC~~ | ||
====== | ====== | ||
+ | |||
----- | ----- | ||
+ | |||
+ | ===== Format specification ===== | ||
The potential format '' | The potential format '' | ||
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=== type === | === type === | ||
- | The '' | + | The '' |
the analytic function. To enable the smooth cutoff option '' | the analytic function. To enable the smooth cutoff option '' | ||
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# Lennard-Jones with smooth cutoff option enabled | # Lennard-Jones with smooth cutoff option enabled | ||
- | type morse_sc | + | type lj_sc |
epsilon 1 0 2 | epsilon 1 0 2 | ||
sigma 1 0 2 | sigma 1 0 2 | ||
h 1 0 2 | h 1 0 2 | ||
</ | </ | ||
+ | |||
+ | All list of all supported analytic potential functions is available [[models: | ||
=== cutoff === | === cutoff === | ||
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with an identifier for that parameter followed by the starting value, the minimum and maximum value for | with an identifier for that parameter followed by the starting value, the minimum and maximum value for | ||
that parameter. The order of these parameters is fixed, for the implemented analytic functions the order | that parameter. The order of these parameters is fixed, for the implemented analytic functions the order | ||
- | can be found [[: | + | can be found [[models: |
- | ----- | + | Giving three times the same value will remove this parameter from the optimization table and use exactly that value when calculating forces/ |
+ | |||
+ | ---- | ||
+ | |||
+ | ===== Additional features ===== | ||
+ | |||
+ | ==== Global parameters | ||
+ | |||
+ | //potfit// supports global parameters, which can occur in different potentials. With this feature it is possible for any potential to " | ||
+ | To use them, you need a section starting with '' | ||
+ | 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> | ||
+ | #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 for analytic potentials since it ensures that the | ||
+ | potential and its gradient vanish at the desired cutoff radius. | ||
+ | Therefore the potential is multiplied with a cutoff function $\Psi$. | ||
+ | |||
+ | $$V_{SC}(r)=\Psi\left(\frac{r-r_c}{h}\right)V(r)\qquad\text{where}\qquad\Psi(x)=\frac{x^4}{1+x^4}$$ | ||
+ | |||
+ | To enable the smooth cutoff for a potential, '' | ||
+ | |||
+ | <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. | ||
+ | |||
+ | ---- | ||
- | === Example | + | ===== Examples ===== |
<code potfit format_0_example.txt> | <code potfit format_0_example.txt> | ||
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</ | </ | ||
- | A sample format 0 potential file for a binary EAM potential is available | + | Many more examples are available |
potfiles/format0.1537692137.txt.gz · Last modified: 2018/09/23 10:42 by daniel