How to find Quantum Capacitance using DFT calculations? What is the use of DOS in the calculation of Quantum Capacitance using DFT?

I am trying to calculate the reaction enthalpy change of 2H2+O2->2H2O, my plan is to calculate the energy of H2, O2, H2O, respectively, then do the simple math. But I find some papers don't do it as my plan, they calculate the energy of H2, H2O, look up the reaction enthalpy change from the exper...

I am trying to do a DFT calculation of Oxygen atoms with the VASP code. My setting is following the official tutorial on the Oxygen atom of VASP. But it turns out the energy levels of the two spin components are very different, which is obviously wrong. My question is: Why can't DFT describe the...