Conventions and units
Cells vectors are given in ASE style as the rows of the cell matrix
The first index in an edge tuple (
edge_index) is the center atom, and the second (
edge_index) is the neighbor
nequip has no prefered system of units; models, errors, predictions, etc. will always be in the units of the original dataset used.
nequip cannot and does not check the consistency of units in inputs you provide, and it is your responsibility to ensure consistent treatment of input and output units
validation_loss_e, etc.) do not have physical units. Errors (
validation_f_rmse) are always reported in physical units.
Pressure / stress / virials
nequip always expresses stress in the “consistent” units of
energy / length^3, which are not the typical physical units used by many codes for stress.
Training labels for stress in the original dataset must be pre-processed by the user to be in consistent units.
Stress also includes an arbitrary sign convention, for which we adopt the choice that
virial = -stress x volume <=> stress = (-1/volume) * virial.
Training labels for stress in the original dataset must be pre-processed by the user to be in this sign convention, which they may or may not already be depending on their origin.