Writing a fix to print output at evaporation

Here is a list of changes made to the source code:

• These are the new files created: fix_printEvaporate.cpp and fix_printEvaporate.h
• These are the existing files that have been modified: fix_print.cpp and fix_print.h
• These are the methods that have been modified: constructor, destructor, init(), end_of_step()
• These are the parameters used: iregion, idregion
• LAMMPS syntax: fix FIX_NAME GROUP printEvaporate N STRING region R (we'll look at this syntax later in this section)

In this section, we will modify Fix Print to print out specified quantities when an atom enters into a particular region, as might be useful when simulating desorption.

Theory – Evaporation region

When studying the desorption of particles that are adsorbed on a surface, it is assumed that a particle has desorbed when it crosses a certain threshold or enters a certain region, usually located far from the surface where the interaction...