Input for Equation of State (EoS) fitting

Last updated

Jul 25, 2024

Author

Gianfranco Ulian

The input file for the equation of state fitting can be of any extension, albeit .dat should be preferred.

The input file format for equation of state fitting closely resembles that of the EOSFit7 software. 1 An example is reported in the following.

#
# Comment lines start with a '#' character and are ignored by the file parser.
#
JOB
Quartz (Angel et al., 2000)
FORMAT
P V sigmaP sigmaV
DATA
0.001  112.981   1.000E-6 0.002
0.430  111.725   0.008    0.014
0.794  110.711   0.008    0.006
1.651  108.597   0.007    0.007
1.845  108.150   0.007    0.019
1.934  107.974   0.007    0.008
2.629  106.467   0.012    0.008
3.300  105.141   0.007    0.009
3.480  104.831   0.012    0.012
3.780  104.285   0.012    0.010
4.026  103.810   0.009    0.013
4.554  102.939   0.009    0.007
4.819  102.534   0.012    0.012
5.214  101.933   0.010    0.010
5.416  101.592   0.009    0.008
5.737  101.143   0.008    0.011
6.478  100.051   0.012    0.015
6.751   99.677   0.010    0.009
7.192   99.064   0.014    0.012
7.899   98.204   0.009    0.014
8.449   97.545   0.012    0.016
8.905   96.989   0.009    0.017

In the following table, the keywords employed by for EoS analysis are reported, alongside a short description of their functionality.

Mandatory Keywords
FORMAT	Specify what the different data columns represent
DATA	Actual data that will be collected
Optional Keywords
JOB	Short description of the provided data

Keywords description

A detailed description of the data requested for each keyword is reported in the following.

FORMAT

This is keyword is used to specify how the data is reported in the file, namely what each column represents. FORMAT is followed in the next line by sub-keywords indicating the type of data in the input file. Each sub-keyword is separated by at least one white space.

The sub-keywords of FORMAT are showed in the following table.

FORMAT sub-keywords	Related quantity
P	Pressure
V	Unit cell volume
a	a-axis values
b	b-axis values
c	c-axis values
sigmaP	Uncertainties of pressure data
sigmaV	Uncertainties of volume data
sigmaa	Uncertainties of a-axis data
sigmab	Uncertainties of b-axis data
sigmac	Uncertainties of c-axis data

It is expected that pressure data is present, thus the P sub-keyword is mandatory. Also, at least one of the structural information, either volume or axis lenghts, must be present, otherwise Quantas will throw an error.

It is not important the order of the sub-keywords, it is sufficient that the structural data are reported in the same order as in FORMAT.

Note

Please, do not insert comments between FORMAT and the next line.

Warning

FORMAT must be inserted in the input file before DATA, otherwise the software is not able to collect the quantities.

Example

If your input data consists of unit cell volume and a-axis lenghts, and you have the uncertainties only for the latter, you should write:

[...]
FORMAT
P V a sigmaa
[...]

DATA

This keyword informs Quantas that the next block is composed by pressure and unit cell data, as specified by the FORMAT keyword.

Warning

FORMAT must be inserted in the input file after FORMAT, otherwise the software is not able to collect the quantities.

JOB (optional)

This keyword sets some information on the input file, that will be printed by Quantas during the run. This description have to be inserted in the line following this keyword.

Note

Please, do not insert comments between JOB and the next line, otherwise the comment will be employed as data description!

References

1

Angel, R.J., 2010. EOSFit7. Computer Program (http://www.rossangel.com).