models:main
Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revisionNext revisionBoth sides next revision | ||
models:main [2018/09/16 10:47] – ↷ Links adapted because of a move operation daniel | models:main [2018/09/23 18:51] – daniel | ||
---|---|---|---|
Line 1: | Line 1: | ||
+ | ~~NOTOC~~ | ||
====== Potential models ====== | ====== Potential models ====== | ||
---- | ---- | ||
- | //potfit// supports | + | //potfit// supports different ways of defining |
- | There are tabulated | + | Currently //potfit// supports the following models: |
+ | * Analytic potential functions | ||
+ | * KIM interactions | ||
+ | * Tabulated potential functions | ||
+ | |||
+ | ==== Analytic | ||
+ | |||
+ | Analytic potentials use the parameters $\alpha_i$ as arguments to analytic function templates. | ||
+ | A well-known example for this would be the Lennard-Jones potential, which uses two parameters $\epsilon$ | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | Using an analytic form for $V(r)$ allows to define the atomic interaction for all possible distances between atoms with very few parameters compared to tabulated potentials. The problem of local parameters (see [[#Tabulated potentials]]) is also not present, parameters are usually global parameters. In certain cases it is even possible to attribute some physical meaning to individual parameters. | ||
+ | |||
+ | The analytic potential implementation in //potfit// has additional features which are only useful with this kind of interactions. They are described on the [[potfiles::format0|analytic | ||
+ | |||
+ | ==== KIM interactions ==== | ||
+ | |||
+ | #TODO | ||
+ | |||
+ | ==== Tabulated potentials ==== | ||
+ | |||
+ | Tabulated potentials | ||
+ | |||
+ | While this may require more paremeters than the analytic variant it also allows for much greater flexibility | ||
+ | |||
+ | {{ : | ||
+ | |||
+ | A disadvantage of this type of potentials is the locality of the individual potential values. To provide a meaningful and transferable potential //potfit// requires reference data at all distances. If there is no reference data available for a certain distance, the potential value at this sampling point may assume a wide range of values without changing the target function at all. Such behavior is problematic for many optimization algorithms and needs to be watched closely while fitting a potential. Using the '' | ||
- | ^ **tabulated potential** | ||
- | | {{: | ||
- | |< | ||
- | * Many parameters | ||
- | * Local parameters | ||
- | * arbitrary functions | ||
- | </ | ||
- | * few parameters | ||
- | * global parameters | ||
- | * physical meaning | ||
- | </ |
models/main.txt · Last modified: 2019/02/23 09:54 by daniel