A PARAM input data file control a parameter optimization calculation, and control how surveys are run.
Data files have names, in the format <file>.dat. An example of a PARAM data set, "br.dat", is given in the following box:
| Comment | * | |||
| Comment | * Optimize PM8 parameters for a single element | |||
| Comment | * | |||
| Control | Line 1 | set=..\normal\all_ref_data.txt ref=N:\;R:\;L:\ params=..\new\params.txt;br.rp | ||
| Parameters | Line 2 | (br)(All) | ||
| End of parameters | Line 3 | end | ||
| ref. data file names | Line 4 |
Like a MOPAC data set, a PARAM data set can include comment lines. These are lines that start with an asterisk (*). Such lines are completely ignored by PARAM.
A long control line can be split into more lines by adding two characters, a space and an ampersand, to the end of a line. When " &" is present, the next line is read as a continuation of the current line.
Line 1: PARAM Keywords that control the type of job. In the example, three keywords are used, SET, REF, and PARAMS. These keywords indicate that:
The set of reference data file names is in the file
all_ref_data.txt, stored in folder
..\normal.
The reference data files themselves are in folders N:\,
R:\, and L:\.
This is also the order of searching.
The default PM8 parameters are to be replaced using parameters in file
params.txt. The file
params.txt is in folder ..\new
The modified parameters are to be replaced by the parameters in file
br.rp. This file is in the current folder.
Since no method was specified, the approximations and initial set of parameters are those of PM8. This is the default.
Line 2: The parameters to be optimized. Here, all parameters for the element Bromine are to be optimized.
There are default lower and upper bounds for parameters. If the default limits need to be altered, the new limits should be put after the parameter, as in:
alpb_h H 0.9 5
xfac_c H 0.1 5
xfac_n H 0.1 5
xfac_o H
0.1 5
FN21 N 0.5 5
FN21 C 0.5 5
HSP C 0.5 5
xfac_O O 0.1 5
xfac_F F 0.1 5
All entries that modify parameter limits should be put before entries of the type (Br)(all); only the first occurrence of a parameter is used in specifying parameters. There are 60 other parameters, these have names PAR1, PAR2, PAR3, ... PAR9, PAR10, ... PAR60. These are global, this means that they do not apply to any specific atom, but instead apply to phenomena such as dispersion and hydrogen bonds. These parameters can be specified using the following style:
*
* PAR7, PAR8, and PAR9 are parameters for Grimme's "D3"
method
*
PAR7 0.2 1.3 = s3 in subroutine DFTD3
PAR8 12.0 15.0 = alp in
subroutine DFTD3
PAR9 0.5 2.0 = rs6 in subroutine DFTD3
Line 3: The terminator for the list of parameters to be optimized.
Line 4: Blank here, but can contain the set of reference data file names.
| Comment | * | |||
| Comment | * Survey the new method for elements H C N and O | |||
| Comment | * | |||
| Control | Line 1 | set=..\normal\all_ref_data.txt ref=N:\ params=..\new\params.txt only survey | ||
| Parameters | Line 2 | (H C N O)(USS) | ||
| End of parameters | Line 3 | end | ||
| ref. data file names | Line 4 |
Line 1: PARAM Keywords that control the type of job. In the example, five keywords are used, SET, REF, PARAMS, ONLY and SURVEY. These keywords indicate that:
The set of reference data file names is in the file
all_ref_data.txt, stored in folder
..\normal.
The reference data files themselves are in the folder N:\.
No other folders are used, as the survey is over normal compounds.
The default PM6 parameters are to be replaced using parameters in file
params.txt. The file
params.txt is in folder ..\new
only: means that only reference data that contains one or more elements
marked for optimization are to be used in the survey.
survey:
means "run a survey" not a parameter optimization.
Since no method was specified, the approximations and initial set of parameters are those of PM6. This is the default.
Line 2: The set of elements to be used in the survey, here hydrogen, carbon, nitrogen, and oxygen. It is sufficient to use the parameter USS. In a survey, these parameters will not be modified; they are only used as a way of indicating which elements are to be used in selecting systems.
Line 3: The terminator for the list of parameters to be optimized.
Line 4: Blank here, but if SET is not used, then line 4 on should contain the set of reference data file names.