Differences

This shows you the differences between two versions of the page.

--- potential_files [2017/10/24 19:00] – Format 3&4: Final value not varied. pbro
+++ potfiles:main [2018/09/22 13:43] – daniel
@@ Line 66: / Line 66: @@
 The order of the different potential functions for a specific potential can be found on the
 corresponding potential page.
-====  Format 0  ====
-The potential format ''0'' is used for analytical potentials exclusively. All of the above apply here,
-except for the ''#G'' line.
-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
-...
-</code>
-The type keyword has to be followed by the [[analytic_functions|unique identifier]] for
-your potential. You can also enable the smooth cutoff option by adding a ''_sc'' at the end. After
-the ''cutoff'' keyword the cutoff radius for this potential has to be given. This is independent for
-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 [[analytic_functions|here]].
-A sample format 0 potential file for a binary system with an EAM potential is available
-{{format_0.pot.txt|here}}.
-====  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
-<code>x_begin x_end steps</code>
-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 ''#G'' header line is specified, each data block must be preceded by two values specifying 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_3g.pot.txt|with}} or {{format_3.pot.txt|without}} the ''#G'' header line.
-====  Format 4  ====
-As with potential files in format 3 each data column has its own spacing. But with potential format
-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
-<code>
-r_0     f(r_0)
-r_1     f(r_1)
-...
-r_steps f(r_steps)
-</code>
-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
-{{format_4g.pot.txt|here}} (with the ''#G'' header line).