Help with Gaussian Calc: P_Sigma & P_Pi Overlap Integrals

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In summary: Forum memberIn summary, the conversation discusses a Gaussian novice's need for assistance in calculating p_sigma and p_pi overlap integrals for metal/noble gas combinations. Suggestions are given for online resources such as the Gaussian website, YouTube tutorials, and online forums to help with finding examples of code and troubleshooting any issues.
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luiz1
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Hello Forum,
Gaussian novice here with some experience of GaussView. I want to use the Gaussian software to calculate the p_sigma and p_pi overlap integrals for some metal/noble gas combinations.

We do not have Foresman and Frisch in our university library and I wanted to know if there is a good resource online to help me get started. What would be ideal would be a few examples of code for a similar calculation which I could use as a guide. Does anyone have any ideas where I could find this, or if it is simple enough, examples of the code itself.

Regards,
L
 
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  • #2
ila

Hello Lila,

Thank you for reaching out to the forum with your question. As a fellow scientist who has experience with Gaussian software, I may be able to offer some guidance. While Foresman and Frisch is a helpful resource, there are other online resources that can also assist you in your calculations.

One option is to visit the Gaussian website and access their online documentation. They have a section specifically dedicated to the overlap integral calculations, which includes theory and examples of code for different types of calculations. Another option is to search for tutorials or guides on YouTube, as there are many helpful videos created by users of Gaussian software.

Additionally, there are online forums and communities where scientists and researchers share their experiences and knowledge with Gaussian software. These forums can be a great resource for finding examples of code and troubleshooting any issues you may encounter.

I hope this helps you get started with your calculations. Best of luck in your research!


 

1. What is a Gaussian calculation?

A Gaussian calculation is a computational method used in quantum chemistry to determine the electronic structure and properties of molecules and materials. It involves solving the Schrodinger equation using Gaussian functions, which are mathematical expressions that describe the probability of finding an electron at a certain point in space.

2. What are P_Sigma & P_Pi overlap integrals?

P_Sigma and P_Pi overlap integrals are mathematical quantities used in Gaussian calculations to determine the overlap between two atomic orbitals. P_Sigma refers to the overlap between two s-orbitals, while P_Pi refers to the overlap between two p-orbitals. These integrals are important in calculating the bonding and antibonding interactions between atoms in a molecule.

3. How are P_Sigma & P_Pi overlap integrals calculated?

P_Sigma and P_Pi overlap integrals are calculated by integrating the product of two Gaussian functions over all space. This integration can be done analytically for simple cases, but for more complex molecules, numerical methods are used to approximate the integrals.

4. What is the significance of P_Sigma & P_Pi overlap integrals?

P_Sigma and P_Pi overlap integrals play a crucial role in determining the molecular orbitals and electronic structure of molecules. They provide information about the strength of bonding and antibonding interactions between atoms, which ultimately affect the stability and reactivity of a molecule.

5. Can P_Sigma & P_Pi overlap integrals be negative?

Yes, P_Sigma and P_Pi overlap integrals can be negative. This indicates that the two atomic orbitals are out of phase and have a repulsive interaction, rather than a bonding one. Negative overlap integrals are often associated with antibonding interactions and can weaken the overall bonding in a molecule.

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