Workflow Overview

This project — Excitonic Properties of Monolayer Black Phosphorus: Critical Role of Electronic Exchange —
follows a four-step workflow to analyze UV-Vis spectra, binding energies, and excitonic properties using hybrid functionals and TDDFT methods.

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Step 1 — Geometry Optimization with PBE_sol

Optimize the initial crystal structure using the PBE_sol functional.

• Input: CP2K optimize_type input file
• Output: Optimized structure for use in Step 2

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Step 2 — Re-optimization with Hybrid Functionals

Use the geometry from Step 1 as input and perform structure optimizations using various hybrid functionals (e.g., PBE0, B3LYP, CAM-B3LYP, etc.).

• Purpose: Evaluate how the choice of functional influences structure-dependent electronic properties
• Note: Since hybrid functional calculations may not converge easily, an initial-guess wavefunction (.wfn) file is used in the input to assist the SCF convergence process.

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Step 3 — TDDFT Calculation (50 States)

Perform TDDFT (Time-Dependent Density Functional Theory) calculations on the structures from Step 2.

• Note: TDDFT calculations also use an initial guess for improved SCF convergence.
• Goal: Obtain excited-state information, including:
  • UV-Vis absorption spectra
  • Binding energy
  • Sr index
  • Natural Transition Orbital (NTO) contributions

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Step 4 — Data Visualization

Use Multiwfn and Python scripts to visualize and analyze the results.

• Generate spectrum_curve.txt and spectrum_line.txt for UV-Vis spectra
• Plot binding energy based on the difference between the fundamental gap and optical gap
• Analyze the correlation between Sr index, NTO contributions, and optical gap

Files: All raw spectral data are provided in UV_vis.tar.gz

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