Heisenberg Energies

Bethe Ansatz 1D energies per bond

PBC: E = -log(2) ≈ -0.693147180559945

OBC: E = 1/4 - log(2) ≈ -0.443147180559945

Energies from DMRG for OBC systems:

o 4x4 E=-9.18920706519297 trunc=-2.22044604925031e-16
o 6x6 E=-21.7267855836853 trunc=3.84443288314884e-09
o 8x8 E=-39.6176792237202 trunc=8.82673760804753e-07

Energy from NLC:

o 4x4 E=-9.189207065