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How to plan your calculations

  1. Problem identification
    1. What properties do you need to know to be able to solve the problem? 1. What is the compound? - structure 2. Has this been investigated before? 1. Literature 2. Databases 3. Previous studies, such as NIST
    2. Is the geometry of the compound available? 1. If yes, this geometry can serve as your initial best guess 2. If no, you need to determine and optimise the structure first
  2. Obtain molecules
    1. Build from its chemical structure (this is the initial guess) 1. Using a visual tool 2. Using cartesian coordinates 3. Using a Z-matrix (internal coordinates) 1. This can be further optimised with UFF, semi empirical calculations, low level ab initio calculations
    2. Download from the internet 1. Using online databases (molview, NIST, ChemDraw) 2. Libraries 3. Article supplementary information
  3. Select your model/theory/basis sets and calculate
    1. Optimisation first - always 1. Allows you to determine the most stable structure for the molecule 2. Can determine if there are isomers involved
    2. Properties next 1. Energy and orbitals 2. Dipoles (FTIR) 3. Charge distributions 4. Further spectroscopy