Actinide Complexes: Example Case Study

This case study demonstrates how to use SPECI for speciation analysis of actinide complexes, specifically a uranium–tert-butoxide system. The example follows the workflow in the CASE2_UOtbu folder and illustrates the use of input files, structure generation, and output analysis.

Directory Overview

The example folder (CASE2_UOtbu) contains:

  • components-data.csv — Main input describing the fragments in the system.

  • ct/ — ChemDraw structure files for each component (in .ct format).

  • xyz/ — Generated 3D structures for all enumerated species (in .xyz format).

  • com/ — Gaussian input files for quantum chemical optimization of selected structures.

  • atom_energy_index_combined_output.csv — Parsed energy output file summarizing computed energies for each structure.

  • logfile.rtf — Execution log and summary.

  • Additional .ct files for each fragment in the root folder.

Input Preparation

1. Edit the `components-data.csv` file:

This CSV specifies the building blocks (fragments), their charge, bonding atoms, and roles. For the uranium–tert-butoxide case, the file looks like:

components,charge,connectivity allowed,donor atom,type
OtBu,0,"0, 1, 2, 3",O,ligand
U,0,"0, 4",U,metal
OtBu,0,"0, 1, 2, 3",O,ligand

2. Place ChemDraw `.ct` files Ensure all fragments listed in the CSV have a matching .ct file, stored in ct/ and/or the root folder (e.g., U.ct, OtBu.ct).

Running the Workflow

3. Run the SPECI workflow using your Jupyter notebook or Python script: Adjust your advanced settings (see the documentation for options like charge_specified, monomers, etc.) as appropriate for your system.

4. Structure Generation: SPECI will enumerate all possible complexes based on your input, generating .xyz files for each unique species in the xyz/ directory. - Each file (e.g., speciation11.xyz) contains atomic coordinates in standard XYZ format and can be visualized with tools like Avogadro or Jmol.

5. Preparing for Quantum Chemical Optimization: For each selected structure, SPECI automatically generates a Gaussian input file (e.g., speciation2.com) in the com/ directory, including resource directives and geometry.

Example .com file excerpt:

%chk=speciation2.chk
%nprocshared=16
%mem=32GB
#p opt=loose PM7 scf=xqc

 speciation study

-1 1
O         -0.13084        1.40090        0.09222
C          0.45868        2.66483        0.40627
...

Note: Edit the Gaussian input as needed for your cluster, memory, or computational method.

Analyzing Output

6. Viewing 3D Structures: Open any .xyz file in the xyz/ folder to inspect the generated actinide complex geometries.

7. Reviewing Energies and Results: After quantum calculations and parsing, SPECI outputs atom_energy_index_combined_output.csv, containing energy values and associated structure indices. This allows rapid ranking and comparison of possible complexes.

Example excerpt:

85_energy,85_index,114_energy,114_index,...
524.68,0,1173.75,1,...

Each column pair gives the computed energy for a structure and its index. Use this file to identify the most stable complexes.

Tips & Best Practices

  • Fragment matching: Names in your CSV and .ct files must match exactly.

  • Visualization: Inspect .xyz files to verify bonding and coordination.

  • Computation: Adjust Gaussian settings for your hardware and use appropriate quantum chemical methods.

  • Result analysis: Use the energy CSV to guide further kinetic or thermodynamic modeling.

References & Further Reading

  • See the [General Input Files](general_input_files.html) and [General Output Files](general_ouput_files.html) documentation for more information about file formats.

  • For troubleshooting or more complex systems (e.g., polynuclear actinide clusters), consult the SPECI [README](https://github.com/Manting-Mu/OLIGO) and example notebooks.