Update README.md

README.md

@@ -23,19 +23,26 @@ pip install git+https://github.com/ACEsuit/mace.git
 
 ```python
 from mace.calculators import MACECalculator
+from ase import Atoms
 from ase.md.npt import NPT
 
+atoms = Atoms("NaCl")
+
 calculator = MACECalculator(
   model_paths=/path/to/pretrained.model,
   device=device
 )
 
-nvt = NPT(
+atoms.calc = calculator
+
+npt = NPT(
   atoms=atoms,
   timestep=timestep,
   temperature_K=temperature,
   externalstress=externalstress,
 )
+
+npt.run(steps)
 ```
 
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