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Lessons Lesson 1

Lesson 1 - Intro to Computational Chemistry

Written by Jeremy Schroeder

What is Computational Chemistry? This is a very loaded question that I hope to briefly answer during this lesson.

Powerpoint For Intro to DFT

Click here to look at a powerpoint created for Intro To DFT.

History of Computational Chemistry

Computational Chemistry has been a research industry since computers were created. It coincides after the creation and discovery of quantum mechanics because it is defined by quantum mechanics in some aspects. The Journal of Computational Chemistry was established in 1980. Now days, it is a very broad field of research with alot of different specific applications and methods.1

Branches of Computational Chemistry

Below is a list of different branches of Computational Chemistry. Each branch has extensive research applications and very detailed definitions. The order of the list is from most computationally intense to least computationally intense.1

  • Coupled Cluster Methods - These methods are used to calculate excited states in any size of system. This method is the most computationally intense because there are many different possible electronic orientations for any one excited electron in a system.

  • Density Functional Theory (DFT) - It is the most computationally intense and complex way to model molecular interactions. There is no time scale and the scope of DFT is at the electron level. It uses fundamental and derived quantum mechanics principles to produce the results. This method is an Ab initio method and solves the Schrödinger equation using equations and definitions that are derived directly from theory. Ab initio means in Latin "from the beginning" and these calculations do not require any experimental data as an input for the calculation. There are many approximations and it is the branch of computational chemistry we use in our research.

  • Molecular Orbital (MO) or Hartree-Fock (HF) Theory - This method is also Ab initio method and is solved using Hartree-Fock Theory equations. It is a simplified version of DFT. At times it is slower than DFT and/or approaches a different answer than DFT but is less computationally intense overall than DFT.

  • Molecular Dynamics - This method looks at forces between atoms and solves Newtonian equations or simplified quantum mechanics equations for atoms in a system. This type of modeling is used to "simulate" what happens at an atomistic level in real time.

  • Monte Carlo - Is similar to Molecular Dynamics but uses sampling methods and configurations of systems to generate new configurations that possibly generate a lower energy.

This picture shows a graph of Computational Chemistry Methods with Calculation Complexity vs Accuracy2.

Branches of Computational Chemistry

Conclusions

There are many different branches and complexities of computational chemistry. This has just been a brief overview to computational chemistry and the main branch we will look at for the other lessons is DFT.

  1. https://en.wikipedia.org/wiki/Computational_chemistry ↩↩

  2. https://www.researchgate.net/figure/Quantum-chemistry-methods-upper-right-are-considered-highly-accurate-but-also-highly_fig2_351530930 ↩