Blog Entry (c) Tuesday, October 22, 2024, by James Pate Williams, Jr. Selected Exercises from “Modern Quantum Chemistry Introduction to Advanced Electronic Structure Theory” by Attila Szabo and Neil S. Ostlund (Dover Books and Kindle)

Source code for the solutions to Exercise 1.18 and 1.19.

Blog Entry (c) Sunday, October 20, 2024, by James Pate Williams, Jr. New and Improved Ab Initio Quantum Chemistry Computations Using the Simple Two Electron Systems: The Helium-Hydrogen Cation and the Hydrogen Molecule

I modified my translation of a FORTRAN program mentioned in a couple of my recent blog entries. The hybrid C/C++ source code is 1,291 lines. I find the basis set of Gaussian Type 1s Orbitals (GTO-NG) using my evolutionary hill-climber, where the GTO1s-NGs curve fit a Slater Type 1s Orbital (STO1s-NG), where N = 4 and 5 in the cation case and N = 4 in the molecule calculation. The percent errors in both cases are considerably less than 1%.

Blog Entry © Monday, October 7, 2024, by James Pate Williams, Jr. Recent Voyages into the World of Quantum Chemistry

Blog Entry © Saturday, October 5, 2024, by James Pate Williams, Jr. Multidimensional Integrals

Electron Probability Distribution Function Etc. (c) James Pate Williams, Jr. December 2023

More than Four Dimensions Why Worry a Blog Entry by James Pate Williams, Jr. December 27, 2023

Some modern physical models of our universe require more than Einstein’s four dimensions: three spatial dimensions and one time dimension. Why do people worry about introducing more dimensions into our understanding of chemistry and physics? When Erwin Schrödinger introduced his famous quantum mechanical two-body solution of the time independent hydrogen-like atom wave equation he went four dimensions to three spatial dimensions. Later, Wolfgang Pauli espoused his famous Pauli Exclusion Principle that simply stated no two electrons (fermions) in an atomic orbital can have the same quantum spin number. Atoms live in a four-dimensional quantum number space augmented by three spatial dimensions and one time dimension.

Some Helium Coulomb Integrals over Six Dimensions by James Pate Williams, Jr. Source Code in C++ Development over December 15 – 16, 2023