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What are common causes of errors in ORCA quantum chemistry calculations?

I'm running DFT and coupled-cluster calculations in ORCA for my molecular systems, and sometimes my results diverge from expected values or literature. As a computational chemist, I know the output is only as good as the input. I'm asking to learn from the collective experience of seasoned users about the less-obvious mistakes in setup, functional choice, or basis set selection that can lead to unreliable data, so I can debug my own workflows more effectively.

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By Suresh Answered 9 months ago

Having supervised many computational projects, I most often see errors stemming from two places. First, a mismatch between the chosen density functional or wavefunction method and the chemical property you're probing like using a poor-dispersion functional for weak interactions. Second, and this is critical, insufficient convergence criteria for the SCF or geometry optimization. I always recommend running tight convergence tests on a model system first; what ORCA accepts by default isn't always publication-ready. Also, never neglect implicit solvation if your system is in solution.

 

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