Decoding heat capacity curves

This is a short introduction on how to analyse and decode heat capacity curve features (D.J. Wales Phys. Rev. E 95, 030105(R), 2017).

After creating your data base of stationary points the analysis of the heat capacity curve is a common next step. To locate the minima contributing to the changes in occupational probability at specific temperatures (i.e. at features in the heat capacity) the following steps should be followed.

First of all you will need to compile the analysis script. It is part of the svn at ~/svn/UTILS/GMIN/Cv.HSA.f90

Then two additional input files are needed:

0.10 2.0 1901 3168 27125

Cv.data

The entries are the lowest and highest temperature for the heat capacity calculations, the number of data points calculated with these limits, the number of degrees of freedom, and the number of minima.

1.3176
0.99

Tanal

Here the first entry is the temperature in the native units of your system (e.g. for AMBER it would be in kcal/mol). The second line quantifies how much of the changes in occupational probability should be accounted for (here it is that all changes sum to 99% of the total change).

Running the script may take some time. At the end ths script should print the following line:

 For disconnectionDPS use line TRMIN 2 27125 min.minus min.plus and
 CHOOSECOLOURS in the dinfo file

Add these two lines to your dinfo file and the contributing minima will be highlighted. A common problem is that the coloured branches are covered by black branches. To get around this problem either change the ps file to move all coloured branches to the end, so they are drawn on top, or increase the line width for the coloured branches.