Understanding 6-31G in Molecules: N2

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In summary, the conversation discusses the use of a 6-31G basis set to study molecules, with a focus on the number of gaussian used for each atom. It is explained that for hydrogen, a basis of two orbitals is used, with one being a contraction of 3 GTO and the other being 1GTO. The original publication on this topic is recommended for further understanding.
  • #1
Hello !

When we say that we use a 6-31G for a molecule (ex: N2), it is this number of gaussian (6+3+1) for both of the atoms or for each atom ?
Thank you
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  • #2
For each atom, obviously, as the gaussians are used to approximate the atomic orbitals of each atom.
  • #3
And how can we explain to use a 6-31G basis set to study a molecule like H2 ? 6 gaussian for the 1s and what about the splitting in 3+1 ?
Thank you again
  • #4

1. What is the significance of 6-31G in molecules?

The 6-31G method is a commonly used basis set in computational chemistry for describing the electronic structure of molecules. It takes into account the atomic orbitals of the atoms in a molecule and allows for accurate calculations of molecular properties such as energy, geometry, and reactivity.

2. How is the 6-31G method applied to the molecule N2?

In the 6-31G method, the electrons in a molecule are represented by a combination of six Gaussian type orbitals (GTOs) for each atom, and the basis set includes 31 functions in total. These functions are used to construct the molecular orbitals for N2, which determine the electronic structure and properties of the molecule.

3. What factors influence the accuracy of 6-31G calculations for N2?

The accuracy of 6-31G calculations for N2 can be influenced by several factors, including the size of the basis set, the level of theory used, and the treatment of electron correlation. The choice of these parameters depends on the specific research question and the desired level of accuracy.

4. How does the 6-31G method compare to other basis sets in studying N2?

The 6-31G method is a relatively simple basis set and is often used as a starting point for more complex calculations. It is considered to be accurate for studying simple molecules like N2, but for more complex systems, larger basis sets and higher levels of theory may be necessary to obtain reliable results.

5. What are the limitations of using the 6-31G method for studying N2?

One limitation of the 6-31G method is that it does not account for all possible electron-electron interactions in a molecule, which can lead to errors in calculated properties. Additionally, the use of a fixed basis set may not accurately capture the electronic structure of molecules with significant electron density variations, such as transition metal complexes.

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