28. Modern Electronic Structure Theory: Basis Sets

TL;DR

Electronic structure theory uses computers and basis sets to approximate solutions to complex problems in chemistry.

Transcript

The following content is provided under a Creative Commons license. Your support will help MIT OpenCourseWare continue to offer high-quality educational resources for free. To make a donation or to view additional materials from hundreds of MIT courses, visit MIT OpenCourseware at ocw.mit.edu. TROY VAN VOORHIS: All right, well, good morning, everyo... Read More

Key Insights

• 🤗 Electronic structure theory relies on computers to solve complex problems in chemistry that cannot be solved by hand.
• 😫 Basis sets are used to approximate the wave functions of electrons, with different levels of accuracy and complexity.
• 😫 Minimal basis sets contain the minimum number of functions necessary to describe the electronic structure, while expanded basis sets improve accuracy by adding more functions.

Questions & Answers

Q: What is the purpose of electronic structure theory?

Electronic structure theory aims to solve complex problems in chemistry by using computers and basis sets to approximate the behavior of electrons in atoms and molecules.

Q: Why do we use basis sets in electronic structure theory?

Basis sets are used to approximate the wave functions of electrons. By using different levels of accuracy and complexity in the basis sets, we can approach the true electronic structure of a system.

Q: What is a minimal basis set?

A minimal basis set contains the minimum number of functions required to describe the electronic structure. It typically includes the necessary valence orbitals of the atoms involved.

Q: How can basis sets be expanded to improve accuracy?

Basis sets can be expanded by adding more functions, such as polarization and diffuse functions. These additional functions cover the electron behavior that is not well-described by the minimal basis set.

Summary & Key Takeaways

• Electronic structure theory relies on computers to solve complex problems that cannot be solved by hand.

• Basis sets are used to approximate the wave functions of electrons in atoms and molecules, with different levels of accuracy.

• Minimal basis sets, such as the single zeta basis set, contain the minimum number of functions necessary to describe the electronic structure.

• Basis sets can be expanded by adding more functions, such as polarization and diffuse functions, to improve accuracy.

• The goal is to approach the complete basis set limit, which is the theoretical result obtained with an infinite number of atomic orbitals.