mace_mp vs MACECalculator, and dispersion #1375

Hi,

I've performed energy optimizations of crystal slabs using ASE and MACE. I first used the ACE command mace_mp to load a local copy of a model (MH-1 with the omol head), and set some parameters (see below for details). Then, I tried using the command MACECalculator instead. Both commands were used with the same model file, and the same parameters, and the same input structures. Turns out the energies I get with the two commands and for the same input geometries, are very different. The absolute values differ by two orders of magnitude. Relative values (eventually I calculate surface energies) still differ by about a factor 2 (with error bars that are much smaller than that). I have a couple of questions:

1. Am I supposed to use mace_mp or MACECalculator to load/initialize the model, what is the difference between these two commands?
2. I understand the MH-1 model with the omol head was pre-trained on OMAT-24 (no dispersion correction) and then fine-tuned using data obtained at the ωB97M-VV10 (with dispersion correction) level of theory. Given that, how am I supposed to deal with dispersion correction, do I want to set that True or False?
3. Is MH-1 + omol the optimial choice for organic solids that are SALTs (organic cation + Cl-), if not what is a better alternative?

Details below, thanks for any help/advice!

michael

the system: an organic molecular crystal, a HCl salt of an nitrogen heterocycle,
the two versions of the command used for loading the model:

1. mace_calc = mace_mp(
   model='/usr/local/models/mace-mh-1.model',
   device="cuda:0"
   head="omol",
   dispersion = False,
   default_dtype="float64"
   )

2. mace_calc = MACECalculator(
   model_paths="/usr/local/models/mace-mh-1.model",
   device="cuda:0"
   default_dtype="float64",
   dispersion = False,
   head="OMOL"
   )