8.3. LAMMPS commands
8.3.1. Enable DeePMD-kit plugin (plugin mode)
If you are using the plugin mode, enable DeePMD-kit package in LAMMPS with plugin
command:
plugin load path/to/deepmd/lib/libdeepmd_lmp.so
The built-in mode doesn’t need this step.
8.3.2. pair_style deepmd
The DeePMD-kit package provides the pair_style deepmd
pair_style deepmd models ... keyword value ...
deepmd = style of this pair_style
models = frozen model(s) to compute the interaction. If multiple models are provided, then the model deviation will be computed
keyword = out_file or out_freq or fparam or atomic or relative
out_file value = filename filename = The file name for the model deviation output. Default is model_devi.out out_freq value = freq freq = Frequency for the model deviation output. Default is 100. fparam value = parameters parameters = one or more frame parameters required for model evaluation. atomic = no value is required. If this keyword is set, the model deviation of each atom will be output. relative value = level level = The level parameter for computing the relative model deviation
8.3.2.1. Examples
pair_style deepmd graph.pb
pair_style deepmd graph.pb fparam 1.2
pair_style deepmd graph_0.pb graph_1.pb graph_2.pb out_file md.out out_freq 10 atomic relative 1.0
8.3.2.2. Description
Evaluate the interaction of the system by using Deep Potential or Deep Potential Smooth Edition. It is noticed that deep potential is not a “pairwise” interaction, but a multi-body interaction.
This pair style takes the deep potential defined in a model file that usually has the .pb extension. The model can be trained and frozen by package DeePMD-kit.
The model deviation evalulate the consistency of the force predictions from multiple models. By default, only the maximal, minimal and averge model deviations are output. If the key atomic
is set, then the model deviation of force prediction of each atom will be output.
By default, the model deviation is output in absolute value. If the keyword relative
is set, then the relative model deviation will be output. The relative model deviation of the force on atom i
is defined by
|Df_i|
Ef_i = -------------
|f_i| + level
where Df_i
is the absolute model deviation of the force on atom i
, |f_i|
is the norm of the the force and level
is provided as the parameter of the keyword relative
.
8.3.2.3. Restrictions
The
deepmd
pair style is provided in the USER-DEEPMD package, which is compiled from the DeePMD-kit, visit the DeePMD-kit website for more information.
8.3.3. Compute tensorial properties
The DeePMD-kit package provide the compute deeptensor/atom
for computing atomic tensorial properties.
compute ID group-ID deeptensor/atom model_file
ID: user-assigned name of the computation
group-ID: ID of the group of atoms to compute
deeptensor/atom: the style of this compute
model_file: the name of the binary model file.
8.3.3.1. Examples
compute dipole all deeptensor/atom dipole.pb
The result of the compute can be dump to trajctory file by
dump 1 all custom 100 water.dump id type c_dipole[1] c_dipole[2] c_dipole[3]
8.3.3.2. Restrictions
The
deeptensor/atom
compute is provided in the USER-DEEPMD package, which is compiled from the DeePMD-kit, visit the DeePMD-kit website for more information.
8.3.4. Long-range interaction
The reciprocal space part of the long-range interaction can be calculated by LAMMPS command kspace_style
. To use it with DeePMD-kit, one writes
pair_style deepmd graph.pb
pair_coeff
kspace_style pppm 1.0e-5
kspace_modify gewald 0.45
Please notice that the DeePMD does nothing to the direct space part of the electrostatic interaction, because this part is assumed to be fitted in the DeePMD model (the direct space cut-off is thus the cut-off of the DeePMD model). The splitting parameter gewald
is modified by the kspace_modify
command.