Hopping barrier: 4×4 square lattice
The chain gave a barrier of
1.16 Ha (31.5 eV), and stepping aside did not help
(−3.52 at one Bohr off-axis, against −3.53 on the ion). That is a property of a
wire: a line of atoms has no route from one interstitial pocket to the next except
through an atom.
A lattice does. Here the carrier travels from the centre of one square, through the
midpoint of a bond, to the centre of the next. That saddle is flanked by two
atoms at half a spacing each — never at zero distance from any of them. This is the
path a real metal offers and a chain cannot.
URL: ?s=0.5 — position along the path, 0 = pocket centre,
0.5 = the bond-midpoint saddle, 1 = next pocket centre. &a=2.5 sets the
lattice spacing, &reset clears the table.
Self-check: s=−0.5 mirrors s=+0.5 about the lattice centre and must agree exactly.
Note s=1 is an edge pocket (vacuum beyond the last column) and is NOT equivalent to
s=0, which is the central one: use s=0 for the pocket energy.
relaxing…