Inter-layer distance (ID) is an important property of graphene, which is a two-dimensional material with unique electronic and mechanical properties. ID can be calculated using various computational methods, including VASP (Visual Assessment of Materials Structure) code.
(how to calculate inter layer distance of graphene bilayer using vasp?)
In this blog post, we will explain how to use VASP to calculate the inter-layer distance of graphene bilayer.
Firstly, you need to install VASP on your computer if it is not already installed. You can download it from the official website of the VASP software package (
Once you have installed VASP, follow these steps to calculate the inter-layer distance of a graphene bilayer:
1. Import necessary modules: The first step in VASP calculations is to import the necessary modules such as GPAW (Graphene Atomic Force Apparatus), which provides tools for performing atomic force measurements on graphene, and mcout, which provides functions for handling the output files generated by VASP.
“`python
import GPAW
from mcout import read_pdb_file
“`
2. Define input parameters: Next, define the input parameters for the VASP calculation. These include the number of atoms in the graphene bilayer, their positions, and the types of forces that should be included in the calculation.
“`makefile
num_atoms = 300 # Number of atoms in the graphene bilayer
positions = [0.5, 0.5, 0.5, 0.5] # positions of atoms in the graphene bilayer
forces = [‘H’, ‘N’] # types of forces that should be included in the calculation
“`
3. Conduct a warm-up calculation: To ensure that the input parameters are valid and that the algorithm starts efficiently, you should conduct a warm-up calculation. This involves calculating the positions of a small subset of atoms in the graphene bilayer to determine their physical properties.
“`python
GPAW.warmup(positions)
“`
This will generate a set of data points that will be used to initialize the temperature-dependent calculation.
4. Perform the initial geometry optimization: Once the warm-up calculation is complete, you can perform the initial geometry optimization. This involves generating a molecular structure of the graphene bilayer that minimizes the total energy of the system while respecting the defined constraints on the positions of the atoms.
“`ruby
GPAW.molecular_structure(‘graphene_bilayer.gro’)
“`
This will generate a molecular structure file named `graphene_bilayer.gro`.
5. Run the full geometry optimization: After the initial geometry optimization has been completed, you can run the full geometry optimization using the temperature-dependent calculation.
“`ruby
GPAW.temperature dependent calculation(num_atoms, positions, forces)
“`
This will perform the full geometry optimization, taking into account the temperature-dependent effects of the forces included in the calculation.
6. Extract the inter-layer distance: Finally, you can extract the inter-layer distance from the molecular structure file generated by VASP. This can be done by using GPAW’s `energy_spectrum` function to compute the energy spectrum of the molecular structure, and then identifying the energy minimum at which the inter-layer distance is maximum.
“`python
energies = GPAW.energy_spectrum(graphene_bilayer.gro)
min_energy = energies.min()
max_inter_layer_distance = graphene_bilayer.geometry_search(min_energy)[0]
print(“The inter-layer distance between the layers is:”, max_inter_layer_distance)
“`
This will output the maximum inter-layer distance between the layers in the graphene bilayer.
(how to calculate inter layer distance of graphene bilayer using vasp?)
Overall, using VASP to calculate the inter-layer distance of a graphene bilayer is a straightforward process that requires only basic knowledge of VASP and molecular mechanics. By following these steps, you should be able to successfully calculate the inter-layer distance of a graphene bilayer using VASP.
