# SCAN-RVV10 geometry optimization

I'm using SCAN-RVV10 to optimize the hexagonal-BN but the optimized geometry doesn't look true as the calculated interlayer distance is far smaller than the experimental value(exp=3.35 Aangstrom, calc=3.20 Angstrom). (SCAN-RVV10 is known as one of the best methods which take into account missing van der Waals interactions.)

My input parameters:

EDIFF = 1E-6
EDIFFG = -1E-2

ISMEAR = 0 ; SIGMA = 0.05

ENCUT = 600

NSW = 100
ISIF = 3
IBRION = 2

METAGGA  = SCAN
LUSE_VDW = .TRUE.
BPARAM = 15.7
LASPH = .TRUE.

NPAR = 32
KPAR = 16


What am I doing wrong? Is there any published interlayer distance for bulk hBN and/or Graphite interlayer distance calculated using SCAN-RVV10?

• At what temperature are the experimental lattice parameters measured? – ProfM Mar 5 at 16:49
• Probably at room temperature. I got your point but other dispersion correction methods (D3, TS, etc) also find close value to the experimental value. – Savir Mar 5 at 17:00
• I have now added an answer. – ProfM Mar 5 at 18:45
• @Savir Your system is two-dimensional? If so, you can't use the ISIF=3 strategy. – Jack Mar 9 at 12:35
• I recently compared a huge variety of DFT methods for predicting 0 K lattice constants of lithium halides (dispersion turns out to play a big role here). SCAN-rVV10 was not the best, TMTPSS-rVV10 was most accurate for both lattice energies and lattice constants. You might consider trying some alternative functionals. – CuriousChemStudent Mar 13 at 22:43