potfiles:main
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The order of the different potential functions for a specific potential can be found on the | The order of the different potential functions for a specific potential can be found on the | ||
corresponding potential page. | corresponding potential page. | ||
- | |||
- | ==== Format 0 ==== | ||
- | |||
- | The potential format '' | ||
- | except for the ''# | ||
- | |||
- | Every analytic potential has to be specified as follows: | ||
- | |||
- | <code potfit> | ||
- | 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 [[: | ||
- | your potential. You can also enable the smooth cutoff option by adding a '' | ||
- | the '' | ||
- | every potential and can thus be different for different potentials. The next line starting with # is | ||
- | a comment which is written by //potfit//. It indicates the minimum neighbor distance for this interaction. | ||
- | Following these lines, the values for the analytic parameters have to be specified. Each line starts | ||
- | 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 | ||
- | can be found [[: | ||
- | |||
- | A sample format 0 potential file for a binary system with an EAM potential is available | ||
- | {{: | ||
- | |||
- | ==== Format 3 ==== | ||
- | |||
- | 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. The | ||
- | argument x is either the atom distance, or the host electron density. These n lines are then followed | ||
- | by n blocks with the function values, one for each atom type pair or atom type. The spacing of function | ||
- | values is computed from the begin, end, and number of function values of the corresponding table and | ||
- | can be different for the different data columns. | ||
- | |||
- | If the ''# | ||
- | gradient of the function at the lower and upper boundaries. A value of 10^30 or higher triggers the | ||
- | usage of natural splines (curvature 0 at boundaries). You should not make the gradient variable at | ||
- | boundaries where natural splines are specified. This will lead to undesired results. | ||
- | |||
- | For potential functions that are a function of distance (e.g. pair potentials, EAM transfer functions), a smooth cutoff at the final sampling value is assumed and the value is not varied. | ||
- | |||
- | A sample format 3 potential file for a binary system for an EAM potential is available | ||
- | {{: | ||
- | |||
- | ==== 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 be equidistant is dropped. Arbitrarily spaced sampling | ||
- | points are possible, but the sampling points have to be given in order. | ||
- | |||
- | Preceding the data columns is a header with one line per column, containing the number of sampling | ||
- | points in the corresponding column. Seperated by blank lines then the data columns follow. Each of | ||
- | the columns has the form | ||
- | |||
- | < | ||
- | 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. | ||
- | |||
- | Similarly as for format 3, for potential functions that are a function of distance (e.g. pair potentials, EAM transfer functions), a smooth cutoff at the final sampling value is assumed and the value is not varied. | ||
- | |||
- | |||
- | A sample format 4 potential file for a binary system (EAM potential) is available | ||
- | {{: | ||
potfiles/main.txt · Last modified: 2018/09/24 17:29 by daniel