# Input file reference¶

This section describes how to use input files to run your simulations with Lumol. An input file contains all information that you need to run a simulation and it is usually organized in four main sections: input, log, systems and simulations.

• The input section contains metadata about the input itself (i.e. a version number).
• The log sections explains different methods about how Lumol reports information about your simulation such as warnings and errors.
• The systems section contains information about the initial configuration, the interactions between atoms and the simulation cell.
• The simulations section defines how your system will propagate. You can generally choose between molecular dynamics (MD), Monte-Carlo (MC) and energy minimization.

Lumol’s input files use the TOML format, a simple and minimalist configuration format based on key = value pairs. You can read an introduction to the TOML format here.

Example:

# an example input file for a Monte Carlo simulation

# input section
[input]
version = 1

# log section
[log]
target = "lumol.log"

# systems section
[[systems]]
file = "data/ethane.xyz"
guess_bonds = true
cell = 100.0

[systems.potentials.global]
cutoff = "14.0 A"
tail_correction = true

[[systems.potentials.pairs]]
atoms = ["C", "C"]
lj = {sigma = "3.750 A", epsilon = "0.814821 kJ/mol"}
restriction = "InterMolecular"

[[systems.potentials.bonds]]
atoms = ["C", "C"]
null = {}

# simulations section
[[simulations]]
nsteps = 1_000_000
outputs = [
{type = "Energy", file = "ethane_ener.dat", frequency = 500},
{type = "Properties", file = "ethane_prp.dat", frequency = 500}
]

[simulations.propagator]
type = "MonteCarlo"
temperature = "217.0 K"
update_frequency = 500

moves = [
{type = "Translate", delta = "20 A", frequency = 50, target_acceptance = 0.5},
{type = "Rotate", delta = "20 deg", frequency = 50, target_acceptance = 0.5},
{type = "Resize", pressure = "5.98 bar", delta = "5 A^3", frequency = 2, target_acceptance = 0.5},
]