Matter Modeling Asked by Michael F. Herbst on August 19, 2021
Plenty of standard plane-wave codes are able to compute correlation energies on top of DFT solutions using the random-phase approximation (RPA). I was wondering what the typical capabilities are in terms of scaling (Default RPA is O(N^4), but approximations can lower it) and the largest systems the codes report to be treatable. I am most strongly focused on open-source codes.
Sorry for the delay. The most recent capabilities I am aware of using VASP version 6 (not open source unfortunately) includes calculation of single point energies, geometry optimizations (some caveats here exist in terms of how strongly variational principle is captured), and I think also phonon calculations. Interestingly, VASP6 has an O(N^3) scaling. This means depending upon the computational resources available, one can model several hundred atoms in the unit cell. I am sure VASP manual has more technical details on this.
If one only wants to do single point energy calculations here, it would be important to benchmark or understand how much the RPA energies will depend unit cell parameters that was obtained from a particular DFT flavor.
Answered by gogo on August 19, 2021
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