DFT: mid-life crisis

Doing DFT is fun: it's fast, easy, black-box, and you never know if your numbers are "predictive". Sometime your favorite functional works, sometime it fails miserably (and you hide the results). Deal with it! In this post, I'm not going to present any calculations. I want to propose my new TV show! Now DFT is… Continue reading DFT: mid-life crisis

Should we really worry about anharmonicity?

My colleague, Dr. Matas, asked herself a question. For a very shallow minimum on the potential energy surface (PES), is the¬†quantum harmonic oscillator approximation (or rigid-rotor-harmonic-oscillator (RRHO)) still valid? Should we worry about its error, especially when calculating the entropy and free energy, which is extremely sensitive with respect to very small vibrational frequencies? The… Continue reading Should we really worry about anharmonicity?