Fix MODELS.md: bare-1/r Coulomb for non-periodic, drop size-consistency note

s11doh8x trains with CoulombModule defaults (no erf damping); the
non-periodic Coulomb path is bare 1/r, not erf-damped. Also drops the
size-consistency wording from the head description.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: timduignan

MODELS.md

@@ -16,7 +16,7 @@ See below for more explanation of this naming convention. Both models have `inf`
 
 * `orbmol-v2`
 
-OrbMol-v2 extends the OrbMol architecture with **learnable per-atom electrostatics**: a `LatentChargeHead` predicts per-atom partial charges (constrained to sum to the system total charge), a `LatentSpinHead` predicts per-atom spins (constrained to sum to 2S = `spin_multiplicity − 1`), and a `CoulombModule` adds a long-range Coulomb energy on top of the GNN — direct erf-damped sum for non-periodic systems, Particle Mesh Ewald via `nvalchemiops` for periodic systems. The energy head (`ChargeConditionedEnergyHead`) is conditioned on the predicted charges and spins per-atom and uses sum-pooling to preserve size-consistency.
+OrbMol-v2 extends the OrbMol architecture with **learnable per-atom electrostatics**: a `LatentChargeHead` predicts per-atom partial charges (constrained to sum to the system total charge), a `LatentSpinHead` predicts per-atom spins (constrained to sum to 2S = `spin_multiplicity − 1`), and a `CoulombModule` adds a long-range Coulomb energy on top of the GNN — direct bare-1/r Coulomb sum for non-periodic systems, Particle Mesh Ewald via `nvalchemiops` for periodic systems. The energy head (`ChargeConditionedEnergyHead`) is conditioned on the predicted charges and spins per-atom.
 
 Trained on OMol25 (ωB97M-V/def2-TZVPD); supports both periodic and non-periodic systems. Stress is enabled via `model.enable_stress()` if needed.