Dear CP2K Community, As a newcomer to CP2K (my experience is with VASP, GPAW, and Quantum Espresso), I have been exploring CP2K's capabilities, particularly for modeling low-spin bi- and tri-radical states of crystal defects through ROKS (Restricted Open-Shell) calculations for potential energy surface analysis. I am pleasantly surprised by this code's performance and capabilities. However, I am slightly confused with ROKS calculations within CP2K, especially regarding the implementation and application of its varying schemes, namely: <ul style="color: rgb(14, 16, 26); background: transparent; margin-top: 0pt; margin-bottom: 0pt;"><li style="background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: disc;">High-Spin ROKS (default ROKS_SCHEME value)</li><li style="background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: disc;">GENERAL (an alternative ROKS_SCHEME value)</li><li style="background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: disc;">Low-Spin ROKS </li></ul>I would greatly appreciate any directed literature or resources that elaborate on these schemes' implementation and practical use. Additionally, I have a few specific inquiries that I hope could be clarified: <ol style="background: transparent; margin-top: 0pt; margin-bottom: 0pt;"><li style="color: rgb(14, 16, 26); background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: decimal;">Is the High-Spin ROKS scheme tailored for single-determinant maximal spin states, where all unpaired electrons align in one spin direction? Can it also model mixed (spin-contaminated) single-determinant states for the von Barth/approximate spin projection method?</li><li style="background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: decimal;">For modeling the doublet state in a triradical scenario, I am considering the following configuration: &LOW_SPIN_ROKS # DOBLET: E(D) = E(Q) - 3/2*E(Q) + 3/2*E(M) ENERGY_SCALING -1.5 1.5 SPIN_CONFIGURATION 1 1 1 # Psi(Q) |a a a> SPIN_CONFIGURATION 1 1 2 # Psi(M) |a a b> &END LOW_SPIN_ROKS Is this the correct approach?</li><li style="color: rgb(14, 16, 26); background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: decimal;">I encountered difficulties running LOW_SPIN_ROKS with the R2SCAN functional (however, it worked with PBE). Are there compatibility issues with meta-GGA functionals?</li><li style="color: rgb(14, 16, 26); background: transparent; margin-top: 0pt; margin-bottom: 0pt; list-style-type: decimal;">Can the energy outcomes from maximal-spin and low-spin calculations be compared to deduce exchange splitting (excitation) energy? </li></ol>I look forward to any recommendations or advice you could provide. Best wishes,Lukas -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/025e1887-09f0-4460-a1ae-24662777baf9n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/025e1887-09f0-4460-a1ae-24662777baf9n%40googlegroups.com</a>.