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Spin–Spin Coupling Constant: Overview

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In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
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Updated: Jun 18, 2025

Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

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Published on: April 8, 2020

A new computational framework for spinor-based relativistic exact two-component calculations using contracted basis

Chaoqun Zhang¹, Kirk A Peterson², Kenneth G Dyall³

¹Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.

The Journal of Chemical Physics

|August 1, 2024

Summary

A new computational framework for relativistic exact two-component (X2C) calculations is introduced using a novel spin-orbit contraction scheme. This method accurately predicts molecular properties, enhancing relativistic quantum chemistry computations.

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Computation of Atmospheric Concentrations of Molecular Clusters from ab initio Thermochemistry

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Generation and Coherent Control of Pulsed Quantum Frequency Combs

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Area of Science:

Computational Chemistry
Quantum Chemistry
Relativistic Calculations

Background:

Relativistic effects are crucial for accurate electronic structure calculations, especially for heavy elements.
Exact two-component (X2C) methods offer a balance between accuracy and computational cost.
Developing efficient computational frameworks for X2C calculations remains an active research area.

Purpose of the Study:

To develop a new computational framework for spinor-based relativistic exact two-component (X2C) calculations.
To implement a j-adapted spin-orbit contraction scheme for improved accuracy.
To validate the framework using benchmark calculations on p-block elements.

Main Methods:

Development of a computational framework for X2C calculations.
Construction of generally contracted, j-adapted basis sets using primitive functions.
Application of atomic mean-field spin-orbit integrals (X2CAMF scheme).
Utilizing contraction coefficients from atomic X2CAMF Hartree-Fock spinors.

Main Results:

Accurate prediction of spin-orbit splittings.
Precise determination of equilibrium bond lengths.
Reliable calculation of harmonic vibrational frequencies.
Demonstration of the accuracy and efficacy of the j-adapted spin-orbit contraction scheme.

Conclusions:

The developed computational framework and j-adapted spin-orbit contraction scheme are accurate and efficient.
This approach provides a reliable method for relativistic quantum chemistry.
The framework enhances the capability of X2C calculations for molecular property predictions.