April 2019 Limerick Project

Computational Chemistry

“Exploring with chem computational
Lets you quantify features foundational. 
Choose objectives; target
Method and basis set. 
(Some calcs close with a quote motivational!)”  

The 13 April 2019 limerick provides an overview of computational chemistry, a field that explores the overlap of chemistry, math, physics, and computer science.  

“Exploring with chem computational/
Lets you quantify features foundational.” 
Computational chemistry is a field that encompasses a wide range of research. One common type of calculation quantifies the properties and features of a chemical species based on its molecular geometry (how are the component atoms connected in space, when a molecule is in its lowest-energy arrangement?).   

For instance, water has a simple molecular structure: a central oxygen atom bonded to two hydrogen atoms, making an overall “V” shape.  What happens to the energy of a water molecule if we stretch out one of the O-H bonds?  The molecule will become less stable, and the molecule’s energy will rise.  A geometry optimization reverses this analysis: manipulating a molecule’s geometry until a minimum energy is achieved.         

Once a molecule is optimized, we can evaluate many useful, fundamental properties.  For the water example, we could calculate its geometric parameters (bond lengths, bond angles), its thermodynamic quantities (energies and related functions), and other simulated experimental data, given an optimized geometry and a related calculation called a frequency analysis.      

“Choose objectives; target/ Method and basis set.”  
Several computational approaches are possible, given the desired research question (i.e., the objectives).  For many of these approaches, you choose a method and basis set that together are best targeted to the type of research question of interest.  The method explains how the calculation will be solved; the basis set explains how many mathematical functions will be involved in that calculation.     

“(Some calcs close with a quote motivational!)”
Many different computational chemistry software packages exist; one of these famously closes each calculation with a philosophical quote