must not have folders names differing only in case: "MC" versu "mc"

This is causing problems on MacOS and Windows with case preserving
but case insensitive file systems.

examples/MC-LOOP/README

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+This directory has an input script that illustrates how to use LAMMPS
+as an energy-evaluation engine in a Monte Carlo (MC) relaxation loop.
+It is just an illustration of how to do this for a toy 2d problem, but
+the script is fairly sophisticated in its use of variables, looping,
+and an if-the-else statement which applies the Boltzmann factor to
+accept or reject a trial atomic-displacement move.
+
+The script sets up a perfect 2d hex lattice, then perturbs all
+the atom positions to "disorder" the system.  It then
+loops in the following manner:
+
+pick a random atom and displace it to a random new position
+evaluate the change in energy of the system due to
+  the single-atom displacement
+accept or reject the trial move
+if accepted, continue to the next iteration
+if rejected, restore the atom to its original position
+  before continuing to the next iteration
+
+The 6 variables at the top of the input script can be adjusted
+to play with various MC parameters.
+
+When the script is finished, statistics about the MC procedure
+are printed.
+
+Dump file snapshots or images or a movie of the MC relaxation can be
+produced by uncommenting the appropriate dump lines in the script.
+
+See the Python script mc.py in python/examples for similar
+functionality encoded in a script that invokes LAMMPS as a library.

examples/MC-LOOP/in.mc

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+# Monte Carlo relaxation of perturbed 2d hex lattice
+
+# set these parameters
+# make sure neigh skin > 2*deltamove
+
+variable iter loop 3000            # number of Monte Carlo moves
+variable deltaperturb equal 0.2    # max size of initial perturbation per dim
+variable deltamove equal 0.1       # max size of MC move in one dimension
+variable density equal 1.0         # reduced LJ density of atoms on lattice
+variable kT equal 0.05             # effective T in Boltzmann factor
+variable seed equal 582783         # RNG seed
+
+# problem setup
+
+units		lj
+atom_style	atomic
+atom_modify     map array sort 0 0.0
+
+dimension       2
+
+lattice		hex ${density}
+region		box block 0 10 0 5 -0.5 0.5
+
+create_box	1 box
+create_atoms	1 box
+mass		1 1.0
+
+pair_style	lj/cut 2.5
+pair_coeff	1 1 1.0 1.0 2.5
+pair_modify     shift yes
+
+neighbor	0.3 bin
+neigh_modify	delay 0 every 1 check yes
+
+variable        e equal pe
+
+# run 0 to get energy of perfect lattice
+# emin = minimum energy
+
+run             0
+variable        emin equal $e
+
+# disorder the system
+# estart = initial energy
+
+variable        x atom x+v_deltaperturb*random(-1.0,1.0,${seed})
+variable        y atom y+v_deltaperturb*random(-1.0,1.0,${seed})
+
+set             group all x v_x
+set             group all y v_y
+
+#dump		1 all atom 25 dump.mc
+
+#dump		2 all image 25 image.*.jpg type type &
+#		zoom 1.6 adiam 1.0
+#dump_modify	2 pad 5
+
+#dump		3 all movie 25 movie.mpg type type &
+#		zoom 1.6 adiam 1.0
+#dump_modify	3 pad 5
+
+variable        elast equal $e
+thermo_style    custom step v_emin v_elast pe
+
+run             0
+
+variable        estart equal $e
+variable        elast equal $e
+
+# loop over Monte Carlo moves
+
+variable        naccept equal 0
+variable        increment equal v_naccept+1
+variable        irandom equal floor(atoms*random(0.0,1.0,${seed})+1)
+variable        rn equal random(0.0,1.0,${seed})
+variable        boltzfactor equal "exp(atoms*(v_elast - v_e) / v_kT)"
+variable        xnew equal x[v_i]+v_deltamove*random(-1.0,1.0,${seed})
+variable        ynew equal y[v_i]+v_deltamove*random(-1.0,1.0,${seed})
+variable        xi equal x[v_i]
+variable        yi equal y[v_i]
+
+label           loop
+
+variable        i equal ${irandom}
+
+variable        x0 equal ${xi}
+variable        y0 equal ${yi}
+
+set             atom $i x ${xnew}
+set             atom $i y ${ynew}
+
+run             1 pre no post no
+
+if              "$e <= ${elast}" then &
+                  "variable elast equal $e" &
+                  "variable naccept equal ${increment}" &
+                elif "${rn} <= ${boltzfactor}" &
+                  "variable elast equal $e" &
+                  "variable naccept equal ${increment}" &
+                else &
+                  "set atom $i x ${x0}" &
+                  "set atom $i y ${y0}"
+
+next            iter
+jump            SELF loop
+
+# final energy and stats
+
+variable       nb equal nbuild
+variable       nbuild equal ${nb}
+
+run             0
+
+print           "MC stats:"
+print           "  starting energy = ${estart}"
+print           "  final energy = $e"
+print           "  minimum energy of perfect lattice = ${emin}"
+print           "  accepted MC moves = ${naccept}"
+print           "  neighbor list rebuilds = ${nbuild}"