Mat Dielectric Response

Dielectric Response

Goal

To calculate the frequency-dependent dielectric response of a crystalline material using atomate2's OpticsMaker and VASP. This includes:

• The independent-particle real and imaginary dielectric functions
• Optical spectra written by the VASP optics workflow
• Post-processing and visualization of the dielectric response

This skill is based on atomate2's optics workflow, which is a flow maker analogous to the band structure workflow.

Instructions

1. Obtain or Prepare the Input Structure

Start with a well-relaxed crystalline structure in CIF or POSCAR format. You can:

• Search Materials Project using the mcp_base_search_materials_project_by_formula tool
• Use a structure from previous calculations
• Create a structure manually using pymatgen or ASE

[!IMPORTANT] The optics workflow assumes a good relaxed bulk structure. Relax the structure first if needed; poor structures will give unreliable optical spectra.

2. Run the Optics Workflow

Use the atomate2 MCP tool with calculation_type="optics":

mcp_atomate2_run_atomate2_vasp_calculation(
    structures_path="structure.cif",        # Input structure file
    output_dir="./optics_results",          # Output directory
    calculation_type="optics",              # Atomate2 optics workflow
    preset_type="omat",                     # VASP preset (omat, mp, matpes-pbe, matpes-r2scan)
    execution_mode="remote",                # "local" or "remote"
    remote_settings={                       # Required for remote execution
        "project": "remote_perlmutter",
        "worker": "perlmutter_worker"
    }
)

The workflow automatically:

1. Runs a static calculation to obtain the charge density
2. Runs the optics calculation to compute the dielectric spectrum

If you need to tune optics settings such as NBANDS, NEDOS, or CSHIFT, pass them through config:

mcp_atomate2_run_atomate2_vasp_calculation(
    structures_path="structure.cif",
    output_dir="./optics_results",
    calculation_type="optics",
    preset_type="omat",
    config={
        "NBANDS": 64,
        "NEDOS": 2000,
        "CSHIFT": 0.1,
    },
    execution_mode="local"
)

3. Post-Process and Visualize Results

After the calculation completes, parse the results and generate a dielectric-response plot:

# Env: base-agent
python .agent/skills/mat-dielectric-response/scripts/plot_dielectric.py \
    optics_results \
    --output dielectric_function.png \
    --mode average

The script will:

• Parse vasprun.xml(.gz) from the atomate2 optics job
• Extract the dielectric spectrum
• Plot the real and imaginary dielectric response

For anisotropic systems, plot the diagonal tensor components separately:

# Env: base-agent
python .agent/skills/mat-dielectric-response/scripts/plot_dielectric.py \
    optics_results \
    --output dielectric_components.png \
    --mode diagonal

4. Manual Inspection of Outputs

If you want to inspect the raw VASP outputs directly, check:

• vasprun.xml or vasprun.xml.gz
• OUTCAR

Search OUTCAR for:

• frequency dependent IMAGINARY DIELECTRIC FUNCTION
• frequency dependent REAL DIELECTRIC FUNCTION
• MACROSCOPIC STATIC DIELECTRIC TENSOR

If you need the static dielectric tensor rather than the frequency-dependent spectrum, search OUTCAR for MACROSCOPIC STATIC DIELECTRIC TENSOR.

Examples

Silicon Carbide Optical Dielectric Response

# 1. Prepare a relaxed SiC structure

# 2. Run optics workflow
mcp_atomate2_run_atomate2_vasp_calculation(
    structures_path="SiC.cif",
    output_dir="./SiC_optics",
    calculation_type="optics",
    preset_type="omat",
    config={
        "NBANDS": 64,
        "NEDOS": 2000,
        "CSHIFT": 0.1,
    },
    execution_mode="local"
)

# 3. Plot results
# Env: base-agent
python .agent/skills/mat-dielectric-response/scripts/plot_dielectric.py \
    SiC_optics \
    --output SiC_dielectric.png \
    --mode average

See examples/ for a SiC dielectric-response tutorial and example plot.

Constraints

• Structure Requirements: Input must be a well-relaxed crystalline structure.
• Workflow Scope: This skill covers atomate2's OpticsMaker workflow for the frequency-dependent dielectric function.
• Local-Field Effects: Advanced manual ALGO=CHI local-field corrections are not part of the atomate2 optics workflow documented here.
• VASP Setup: Requires properly configured VASP and pseudopotentials.
• Atomate2 Setup: Requires atomate2, jobflow, and either local or remote execution configuration.
• Environments:
  • Optics calculation: atomate2-agent
  • Post-processing scripts: base-agent
• Convergence:
  • Increase NBANDS until the optical spectrum is converged over the energy range of interest
  • Check sensitivity to NEDOS, CSHIFT, and k-point density
• Band-Gap Limitation: Semi-local DFT typically underestimates the absorption onset; use hybrid functionals or beyond-DFT methods for quantitative spectra.

Author: ChazzBM3 Contact: musgrave@caltech.edu