jahn-teller-dynamics 0.3.7

Dynamic Jahn-Teller Effect Calculator

Jahn-Teller-Dynamics - Dynamic Jahn-Teller Effect Calculator

Table of Contents

• About the Project
• Installation
• Usage
• Configuration Examples
• Output Options
• Eigenstates

About the Project

A Python tool for calculating dynamic Jahn-Teller effects, spin-orbit interactions, and energy splitting of degenerate electron states from DFT calculations.

The Exe.py script calculates:

• The E⊗e dynamic Jahn-Teller effect
• Spin-orbit interaction
• Energy splitting of degenerate electron states
• ZPL (zero phonon line) shift in magnetic field

This project was built with Python 3.10.

Installation

Installation directly from PyPI:

pip install jahn-teller-dynamics

Installation from Github

1. Download the project:

   git clone https://github.com/tbalu98/Jahn-Teller-Dynamics.git
   

   or download the zip file

2. Install dependencies:

   pip3 install -r requirements.txt
   

Usage

To run a calculation, you need to:

1. Create a configuration file (.cfg) that specifies your Jahn-Teller active system parameters
2. Run the following command, replacing configuration_file.cfg with your config file name:

Exe configuration_file.cfg

Test Data

To test the code, download the config_files and data folder that contains the vasprunxml files for the negatively charged tin vacancy (SnV) from: Google Drive

Configuration Examples

Example configuration files can be found in the config_files folder, which demonstrate different use cases and parameter settings.

1. Basic Configuration with vasprunxml

To perform calculations, you need at least two geometric configurations of your Jahn-Teller active system:

• The highly symmetric geometry
• The Jahn-Teller distorted geometry with minimum energy
• (Optional) The saddle point geometry
• (Optional) Spin-orbit coupling from density functional theory calculation

Example configuration:

[essentials]
maximum_number_of_vibrational_quanta = 12
output_prefix = SnV_gnd
output_folder = results/SnV_results
input_folder = data/SnV_data
eigen_states = real
save_raw_parameters = true
save_model_hamiltonian_cfg = true


[system_parameters]
saddle_point_geometry = SnV_gnd_saddle_point.xml
global_minimum_geometry = SnV_gnd_C2h.xml
high_symmetry_geometry = SnV_gnd_D3d.xml
#spin-orbit coupling obtained from DFT calculation in meV:
#This calculation modells a hole therefore, it is a negative value.
DFT_spin-orbit_coupling = -8.3
orbital_reduction_factor =  0.328

#Optionally you may specify a magnetic field
[magnetic_field]
#In Tesla
minimum = 0.0
maximum = 10.0
direction_vector = 1.0, 0.0, 0.0
step_number = 11

On the command line it presents:

• Jahn-Teller energy
• barrier energy in case of a second order calculation
• Taylor coefficients of the interaction
• Ham reduction factor
• theoretical enegy level splitting

In the output_folder it saves these results into .csv format and the eigen energies and states of the system. If a magnetic field is presented than it saves them for each magnetic field strength.

Example of eigenstate output format:

['x', 'y', 'orbital', 'spin']	eigenstate_1	eigenstate_2	...
|0,0,ex,up>	(1.4e-08-4.62e-08j)	(0.6041025766+0j)
|0,0,ex,down>	(0.6041025766+0j)	(1.106e-07-5.56e-08j)
|0,0,ey,up>	(-4.62e-08-1.4e-08j)	-0.6041025676j
|0,0,ey,down>	0.6041025676j	(5.56e-08+1.106e-07j)
|0,1,ex,up>	(-1.87e-08-5.7e-09j)	-0.2439570653j
|0,1,ex,down>	0.2439570653j	(2.24e-08+4.47e-08j)
...

The eigenstates are named eigenstate_1, eigenstate_2, etc... The corresponding eigenenergies can be found in a separate file:

state_name	eigenenergy
eigenstate_1	42.4731822278
eigenstate_2	42.4731823331
eigenstate_3	46.3897044769
eigenstate_4	46.3897045822
...	...

2. ZPL Calculation Configuration

For ZPL shift calculations, you need to specify:

• Ground and excited states
• Magnetic field parameters
• Basis vectors of the E⊗e dynamic Jahn-Teller active system' spin

[essentials]
maximum_number_of_vibrational_quanta = 12
output_prefix = SnV_ZPL_shift
output_folder = results/SnV_results
input_folder = data/SnV_data
#basis vectors of the Exe system's coordinate system
basis_vector_1 = 1, -1, 0
basis_vector_2 = 1, 1, -2
basis_vector_3 = 1, 1, 1

# It can use the model four state Hamiltonian.
model_Hamiltonian = false


#Saves geometries of the system in .csv files, and creates a corresponding .cfg file
save_raw_parameters = true
#Save a .cfg file which contains the parameters of the model Hamiltonian operator of the system
save_model_Hamiltonian_cfg = true
#Save a .cfg file which contains the Taylor coefficients of the electron-phonon interaction
save_taylor_coeffs_cfg = true
[ground_state_parameters]
saddle_point_geometry = SnV_gnd_saddle_point.xml
global_minimum_geometry = SnV_gnd_C2h.xml
high_symmetry_geometry = SnV_gnd_D3d.xml
#spin-orbit coupling obtained from DFT calculation in meV:
DFT_spin-orbit_coupling = -8.3
orbital_reduction_factor =  0.328


[excited_state_parameters]
saddle_point_geometry = SnV_ex_saddle_point.xml
global_minimum_geometry = SnV_ex_C2h.xml
high_symmetry_geometry = SnV_ex_D3d.xml
#spin-orbit coupling obtained from DFT calculation in meV:
DFT_spin-orbit_coupling = -95.9
orbital_reduction_factor =  0.782


[magnetic_field]
#In Tesla
minimum = 0.0
maximum = 10.0
direction_vector = 1.0, 0.0, 0.0
step_number = 11

3. CSV File Configuration

By opting for the save_raw_parameters = true the program saves the atomic locations in CSV files and creates the corresponding configurational file. It contains additional structural parameters of the lattice energies, lattice vectors, atomic masses and names.

[ground_state_parameters]
dft_spin-orbit_coupling = -8.3
orbital_reduction_factor = 0.328
high_symmetry_geometry = SnV_ZPL_shift_ground_state_parameters_high_symmetry_geometry.csv
high_symmetric_geometry_energy = -5368.30679265
global_minimum_geometry = SnV_ZPL_shift_ground_state_parameters_global_minimum_geometry.csv
global_minimum_energy = -5368.32839163
saddle_point_energy = -5368.32682965
saddle_point_geometry = SnV_ZPL_shift_ground_state_parameters_saddle_point_geometry.csv

[excited_state_parameters]
dft_spin-orbit_coupling = -95.9
orbital_reduction_factor = 0.782
high_symmetry_geometry = SnV_ZPL_shift_excited_state_parameters_high_symmetry_geometry.csv
high_symmetric_geometry_energy = -5366.13656085
global_minimum_geometry = SnV_ZPL_shift_excited_state_parameters_global_minimum_geometry.csv
global_minimum_energy = -5366.21970743
saddle_point_energy = -5366.21291581
saddle_point_geometry = SnV_ZPL_shift_excited_state_parameters_saddle_point_geometry.csv

[atom_structure_parameters]
masses_of_atoms = 118.71, 12.011
names_of_atoms = Sn, C
numbers_of_atoms = 1, 510
basis_vector_1 = 14.17860889, 0.0, 0.0
basis_vector_2 = 0.0, 14.17860889, 0.0
basis_vector_3 = 0.0, 0.0, 14.17860889

[essentials]
maximum_number_of_vibrational_quanta = 12
output_prefix = SnV_ZPL_shift
output_folder = results/SnV_results
input_folder = data/SnV_data
basis_vector_1 = 1, -1, 0
basis_vector_2 = 1, 1, -2
basis_vector_3 = 1, 1, 1
model_hamiltonian = false
save_raw_parameters = false
save_model_hamiltonian_cfg = false
save_taylor_coeffs_cfg = true

[magnetic_field]
minimum = 0.0
maximum = 10.0
step_number = 11
direction_vector = 1.0, 0.0, 0.0

4. Direct Parameter Configuration

You can also specify E⊗e Jahn-Teller interaction parameters directly. There you need to give the Jahn-Teller energies, barrier energies, and the distances between the lattice configurations so the program can calculate the coeffcients of the Jahn-Teller interaction.

[essentials]
maximum_number_of_vibrational_quanta = 12
output_prefix = SnV_ZPL_shift_JT_pars
output_folder = results/SnV_results
spectrum_range = 50

#basis vectors of the Exe system's coordinate system
basis_vector_1 = 1, -1, 0
basis_vector_2 = 1, 1, -2
basis_vector_3 = 1, 1, 1



[ground_state_parameters]
Jahn-Teller_energy = 21.599
barrier_energy = 1.562
vibrational_energy_quantum = 79.4954
#spin-orbit coupling obtained from DFT calculation in meV:
DFT_spin-orbit_coupling = -8.3
orbital_reduction_factor =  0.328
high_symmetric_geometry-minimum_energy_geometry_distance = 0.1644
high_symmetric_geometry-saddle_point_geometry_distance = 0.1676

[excited_state_parameters]
Jahn-Teller_energy = 83.1466
barrier_energy = 6.7916
vibrational_energy_quantum = 75.6121
#spin-orbit coupling obtained from DFT calculation in meV:
DFT_spin-orbit_coupling = -95.9
orbital_reduction_factor =  0.782
high_symmetric_geometry-minimum_energy_geometry_distance = 0.3407
high_symmetric_geometry-saddle_point_geometry_distance = 0.3421



[magnetic_field]
minimum = 0.0
maximum = 10.0
direction_vector = 0.0, 0.0, 1.0
step_number = 11
#basis vector of the magnetic field (the program normalize it automatically)
basis_vector_1 = 14.17860889, 0.0, 0.0
basis_vector_2 = 0.0, 14.17860889, 0.0
basis_vector_3 = 0.0, 0.0, 14.17860889

5. Four-State Model Configuration

For calculations using the four-state model:

[essentials]
maximum_number_of_vibrational_quanta = 12
output_prefix = SnV_ZPL_shift
output_folder = results/SnV_results
input_folder = data/SnV_data
basis_vector_1 = 1, -1, 0
basis_vector_2 = 1, 1, -2
basis_vector_3 = 1, 1, 1
model_hamiltonian = false
save_raw_parameters = false
save_model_hamiltonian_cfg = false
save_taylor_coeffs_cfg = true

[ground_state_parameters]
dft_spin-orbit_coupling = -8.3
orbital_reduction_factor = 0.328
ham_reduction_factor = 0.4706170075391288
delta_p = 0.04700977697171288
k_jt = 0.01040108529115713

[excited_state_parameters]
dft_spin-orbit_coupling = -95.9
orbital_reduction_factor = 0.782
ham_reduction_factor = 0.12550119453836145
delta_p = 0.2967480915488183
k_jt = 0.0644133368548232

[magnetic_field]
minimum = 0.0
maximum = 10.0
step_number = 11
direction_vector = 1.0, 0.0, 0.0

Output Options

The tool can generate various output files based on configuration:

• save_raw_parameters = true: Saves geometries in CSV format and generates the corresponding configuration file with atomic parameters such as chemical symbol, mass, basis vector of the supercell.
• save_model_hamiltonian_cfg = true: Generates four state model Hamiltonian configuration
• save_taylor_coeffs_cfg = true: Saves .cfg files that contains Taylor coefficients for the dynamic Jahn-Teller interaction

Eigenstates

The script can save eigenstates in either real or complex basis:

• Complex basis (e₊, e_-): Superpositions of degenerate orbitals (e_x, e_y)
  • e₊ = -(e_x+ie_y)
  • e_- = e_x-ie_y

To use complex eigenstates, set:

eigen_states = complex

Directory Structure

Jahn-Teller-Dynamics/
├── src/
│   └── jahn_teller_dynamics/          # Main package
│       ├── __init__.py
│       ├── Exe.py                     # Main executable script
│       ├── io/                        # Input/Output modules
│       │   ├── __init__.py
│       │   ├── JT_config_file_parsing.py
│       │   ├── plotting.py
│       │   ├── user_workflow.py
│       │   ├── VASP.py
│       │   └── xml_parser.py
│       ├── math/                      # Mathematical utilities
│       │   ├── __init__.py
│       │   ├── matrix_mechanics.py
│       │   ├── braket_formalism.py
│       │   └── maths.py
│       ├── physics/                   # Physics modules
│       │   ├── __init__.py
│       │   ├── jahn_teller_theory.py
│       │   ├── quantum_physics.py
│       │   └── quantum_system.py
├── config_files/                      # Example configuration files
│   ├── SnV_gnd_csv.cfg
│   ├── SnV_ZPL_shift_csv.cfg
│   └── ... (other config examples)
├── data/                             # Data directory (user-provided)
├── results/                          # Output results directory (user-provided)
├── requirements.txt                  # Python dependencies
├── setup.py                         # Package installation script
└── README.md                        # This file

Key Components:

• src/jahn_teller_dynamics/: Main package containing all Python modules
• io/: Input/Output modules for configuration parsing, VASP file handling, and plotting
• math/: Mathematical utilities for braket formalism and matrix mechanics and Hilbert spaces
• physics/: Core physics modules for Jahn-Teller theory and quantum mechanical systems
• config_files/: Example configuration files for different calculation types
• data/: Directory for user input data (VASP files, CSV files, etc.)
• results/: Output directory for calculation results