ATAT 3.52 + OpenCalphad 6.055: binary teaching regular solution

Run from this directory, in order:
  bash setup.sh
  bash run.sh
  bash plot.sh
  bash inspect.sh
  bash replot.sh
Optional scientific comparison plots:
  /public/toolkit/miniconda3/envs/ase-3.29.0/bin/python code/plot_analysis.py

setup builds bundled unmodified GPL OpenCalphad source using GCC/GFortran,
make -j1, -O2 -fopenmp -fPIC, in .runtime. It copies the installed ATAT
ocplotpd to .runtime and applies two explicit private-only changes:
1. POSIX shell stderr redirection portability.
2. At each T seed an x(Au)=0.5 native equilibrium before continuing to the
   requested composition with calc no_global. This recipe is deliberately
   restricted to this binary symmetric regular solution below its critical
   temperature, and is not a general CALPHAD initialization prescription.

No public installation or ~/.ocplotpd is changed. ATAT script is read from
the public installation at setup time rather than redistributed here.

inputs/regular.tdb is NOT an assessed Cu-Au database or DFT-derived material
dataset. It defines G=RT[x ln x+(1-x) ln(1-x)]+20000*x*(1-x), R=8.31451.
The Cu/Au labels are species names for demonstrating TDB and plotting.
There are 80 T-composition targets and 31 targets at 800 K, plus 111 seed
equilibria; seed=612001. code/validate.py independently solves chemical
potential equality and checks Gibbs energy, phase compositions and mass
balance without replacing the native output values.

reference contains actual outputs from the same model; new-work is freshly
calculated by run.sh. Two composition sets of FCC_A1 are a miscibility gap,
not two different lattice types. ocplotpd writes phase/tie-line plot rows
only for multiphase targets. Single-phase targets remain in alltmp.oco and
analysis/equilibria.csv. Four-decimal sampled composition and OC text output
precision are retained. The gnuplot input uses Au column 6 and T column 4.

Compiler: system GCC/GFortran 13.3.0. CPU only, one thread; no GPU required.
For new material work, choose a licensed, assessed database, valid phases,
elements, temperature and pressure range, and review initialization and
convergence separately. This example is an operational reference.

OpenCalphad source: https://www.opencalphad.com/downloads/OC6055.zip
SHA256 b3c884e3085693516c26f71b7bd774bc6daecfbc4d326eb6708859e7b315bdc2
GNU GPL terms: source/GNU-GPL-v3.pdf and bundled source headers.
ATAT documentation: https://axelvandewalle.github.io/www-avdw/atat/manual.pdf
