potfiles:main
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potential_files [2013/03/01 08:15] – daniel | potfiles:main [2018/09/22 14:29] – daniel | ||
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+ | ~~NOTOC~~ | ||
====== Potential files ====== | ====== Potential files ====== | ||
---- | ---- | ||
- | The interactions | + | The interactions supported by //potfit// are defined in terms of tabulated functions, given by analytic parameters |
+ | |||
+ | Each potential file consists of a header and a body, just like the configurations. While the header format is the same for all supported potentials the body format is fundamentally different for tabulated, analytic and KIM potentials. | ||
+ | |||
+ | For potentials implemented in //potfit// the number | ||
==== Potential File Header | ==== Potential File Header | ||
- | The header is comparable | + | The header |
- | < | + | < |
- | ## this is just a comment line | + | #F < |
- | #F 3 n | + | #T <interaction name> |
- | #T <TYPE> | + | #C <element 0> <element 1> ... |
- | #C Mg Zn | + | #I 0 1 ... n entries |
- | #I 0 1 .... n entries | + | #G 2 3 ... n entries |
- | #G 2 3 .... n entries | + | #E |
- | ## this is another comment line | + | |
- | #E this is the very last header line | + | |
</ | </ | ||
- | Header lines start with the hash character | + | Header lines have to start with the number sign ''#'' |
- | The line starting with #T specifies | + | The second character can be any of the following specifiers. Lines with unknown specifiers will be treated like comments, but it is recommended that such lines start with two ''#'' |
- | The line I defines whether a whole potential function should be kept constant during a force matching run. Each digit corresponds to one function table, so there should be n digits in total. A value of ' | + | Not all specifiers all mandatory, some of them are optional. |
- | The line G specifies whether the gradient of the interpolation splines should be treated as fixed or as an additional degree of freedom. Each digit corresponds to one function table, so there should be n digits in total. The information is bit-coded, ' | + | == #F == |
- | The line C specifies | + | The mandatory format specifier ''# |
+ | It requires two arguments, the format itself and the number | ||
+ | Valid formats | ||
+ | * [[potfiles: | ||
+ | * [[potfiles:format3|Format 3]] - tabulated potentials with fixed spacing | ||
+ | * [[potfiles: | ||
+ | * [[potfiles: | ||
- | < | + | The value for the number of potential functions needs to be the correct value for the selected potential type. |
+ | If the number of atom types in the parameter file is 2 and the potential is '' | ||
+ | |||
+ | == #T == | ||
+ | |||
+ | The optional interaction type specifier ''# | ||
+ | |||
+ | Even though this line is optional, a mismatch in the string and the compiled //potfit// binary will lead to a runtime error. A //potfit// binary compiled for '' | ||
+ | |||
+ | == #C == | ||
+ | |||
+ | The line ''# | ||
+ | read for potentials, it is only given in the output to facilitate the handling of potential files. In | ||
+ | addition there will also be a comment on how the potentials are ordered, for the ternary system AlPdMn | ||
+ | a header for an EAM-potential could look like the following: | ||
+ | |||
+ | < | ||
#F 0 12 | #F 0 12 | ||
#C Al Pd Mn | #C Al Pd Mn | ||
Line 36: | Line 61: | ||
</ | </ | ||
- | The order of the different potential functions for a specific potential can be found on the corresponding potential page. | + | == #I == |
- | ==== Format | + | The line ''# |
+ | matching run. Each digit corresponds to one function table, so there should be n digits in total. A | ||
+ | value of '' | ||
+ | keeps it fixed. This is useful for example if a third component is to be added to a binary system | ||
+ | and only the additional potentials are to be allowed to change. | ||
- | The potential format 0 is used for analytical potentials exclusively. All of the above apply here, except for the G line. | + | == #G == |
- | Every analytic potential has to be specified | + | The line ''# |
+ | or as an additional degree of freedom. Each digit corresponds to one function table, so there should be | ||
+ | n digits in total. The information is bit-coded, '' | ||
+ | '' | ||
+ | This does not apply to analytic potentials. | ||
- | < | + | == #E == |
- | type identifier | + | |
- | cutoff value | + | |
- | # rmin 1.0 | + | |
- | p_1 value min max | + | |
- | p_2 value min max | + | |
- | ... | + | |
- | </ | + | |
- | The type keyword has to be followed by the [[Analytic potentials/ | + | The very last header line must have |
+ | a character | ||
- | A sample format 0 potential file for a binary system with an EAM potential is available [[Media: | + | ---- |
- | ==== Format 3 ==== | + | The order of the different potential |
- | + | corresponding | |
- | In a potential file in format 3, each data column has its own range and spacing. Sampling points are equidistant in the atomic distance r or (when using EAM-type interactions) electron density n. If we have n data columns, the file starts with n lines of the form | + | |
- | + | ||
- | < | + | |
- | + | ||
- | specifying the start, end, and the number of function values in each data set. n data columns. | + | |
- | + | ||
- | If the ' | + | |
- | + | ||
- | A sample format 3 potential | + | |
- | + | ||
- | ==== Format 4 ==== | + | |
- | + | ||
- | As with potential files in format 3 each data column has its own spacing. But with potential format 4 the requirement that the sampling points | + | |
- | + | ||
- | Preceding the data columns is a header with one line per column, containing the number of sampling points in the corresponding | + | |
- | + | ||
- | < | + | |
- | r_0 | + | |
- | r_1 | + | |
- | ... | + | |
- | r_steps f(r_steps) | + | |
- | </ | + | |
- | Please note that $r_0 < r_1 < ldots < r_{steps}$ is required. The order of the columns is the same as with format 3. | ||
- | A sample format 4 potential file for a binary system (EAM potential) is available [[Media: | ||
potfiles/main.txt · Last modified: 2018/09/24 17:29 by daniel