Hello Thomas, 1/2
They haven't specified any parameters to my knowledge that would lead to such a large error. There may be slight difference in the thresholds of energetic convergence, but they should yield errors on a much smaller scale. 2/2 RE: box sizes - We did briefly fall foul of having inconsistent box sizes for one or two calculations, but this is definitely a problem we've addressed. (We use slightly different box sizes for the adsorbate, but I've ran a few different cell sizes for this small molecules and it yielded very small differences). And you're quite right, I do apologise, that should be written as: E_adsorption = E_(slab+adsorbate) - (E_slab + E_adsorbate) Kind regards, Gabriel ________________________________ From: users <[email protected]> on behalf of Tamas Karpati <[email protected]> Sent: 07 October 2020 11:57 To: Quantum ESPRESSO users Forum <[email protected]> Subject: Re: [QE-users] Underestimated Adsorption Energy with optB88-vdW Dear Gabriel, 1/2, are your sims. reproducing *all* of the ref. params? (eg. are cell parameters the same?) any missing params. would contribute by adding an *unknown* magnitude of error... 2/2, my guess would be that your evaluation of dE_a is wrong due to *different cell sizes* (basis set superposition error?); this would explain the systematic character of the deviation and suggest (pain indeed) to increase cell sizes up to the same (ie. the largest) of E_slab+ads, E_slab and E_adsorbant. +1, your eq. for the heat is recursive (kidding): LHS is to be renamed! HTH, t On Wed, Oct 7, 2020 at 12:19 PM Gabriel Bramley <[email protected]> wrote: > > Dear Users, > > Problem: > > I am performing calculations with the optB88-vdW functional to obtain > adsorption energies of small aromatic molecules on metallic surface facets > (Pt(111) and phenol for the cases discussed here). Unfortunately, the > adsorption energies obtained from these calculations are systematically 50 kJ > mol^-1 below comparable studies performed with VASP. I have replicated their > parameters as closely as possible - as such I am also using PBE PAW > pseudopotentials from the psl pseudopotential library. > > The above underestimation occurs for a fully periodic calculation. Using the > dipole corrections (2D and ESM (bc1)) appears to exacerbate these issues, > leading to a 70 kJ mol^-1 underestimation of the adsorption energy. (The > system is centred in the centre of the cell with 8 Ang of vacuum either side > of the system for 2D, and the system is centred around z=0 for ESM). > > The calculation for adsorption energy is performed as: > E_ads = E_slab+ads - (E_slab + E_ads) > Where the adsorbate is calculated in a 30x30x30 Ang cell with the > Markov-Payne dipole correction (Though this give negligable difference > compared to full PBC). > > Question: > > The PBE+rvv10 functional performs significantly better with PBC and 2D > Coulomb Cutoff, giving sensible and expected values for the adsorption > energy. However, I am cautious in trusting these results given the large > errors for the optB88-vdW functional. Is there something obvious I am missing > in these calculations or is this a known issue? > > A previous email to this list has pointed out other issues with this > functional > (https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.mail-archive.com%2Fusers%40lists.quantum-espresso.org%2Fmsg35965.html&data=01%7C01%7CG.A.Bramley%40soton.ac.uk%7Cff146e0c9f8442a6502408d86aaf85d0%7C4a5378f929f44d3ebe89669d03ada9d8%7C0&sdata=XIGDLm5GiwsmCuyJjhxr3hvWbAc7nah5%2BXHAw1JzxHY%3D&reserved=0). > This might help, but could someone please clarify this as well? > > Additional information: > > I am using QE v.6.5 compiled with Intel-2018 with the ELPA 2017 library. > Enivron Module installed but not used in these calculations. All QC tests > pass without error. > > Please find below the input file: > > ___________________________________ > > &CONTROL > calculation = 'relax' > restart_mode = 'from_scratch' > prefix = 'Pt' > disk_io = 'low' > pseudo_dir = '/home/gab1u17/pslib-kj-paw/' > nstep = 300 > / > &SYSTEM > ibrav = 0 > ecutwfc = 45 > ecutrho = 360 > occupations = 'smearing' > degauss = 0.05 > smearing = 'gaussian' > input_dft = 'vdw-df-obk8' > assume_isolated = '2D' > ntyp = 4 > nat = 48 > / > &ELECTRONS > electron_maxstep = 150 > conv_thr = 8e-08 > mixing_mode = 'local-TF' > mixing_beta = 0.2 > / > &IONS > ion_dynamics = 'bfgs' > / > &CELL > / > > ATOMIC_SPECIES > Pt 195.084 Pt.pbe-n-kjpaw_psl.1.0.0.UPF > C 12.011 C.pbe-n-kjpaw_psl.1.0.0.UPF > O 15.999 O.pbe-n-kjpaw_psl.1.0.0.UPF > H 1.008 H.pbe-n-kjpaw_psl.1.0.0.UPF > > K_POINTS automatic > 6 6 1 0 0 0 > > CELL_PARAMETERS angstrom > 7.42718991274627 0.00000000000000 0.00000000000000 > 3.71359495637314 6.43213514316980 0.00000000000000 > 0.00000000000000 0.00000000000000 29.000000000003126 > > ATOMIC_POSITIONS angstrom > Pt 2.5641489000 0.4594382200 8.0000000000 0 0 0 > Pt 5.2167167200 1.3783146700 8.0000000000 0 0 0 > ... > Pt 4.1556895900 0.1531460700 17.1683222700 > Pt 6.8082574200 1.0720225200 17.1683222700 > Pt 2.0336353300 1.9908989700 17.1683222700 > ... > H 0.3060672802 1.6388023741 19.1376040000 > H 2.7167357186 1.0284278006 19.1376040000 > H 4.4562891110 2.8078620154 19.1376040000 > > ___________________________________ > > Thank you in advance for your assistance. > > Kind regards, > Gabriel Bramley > PhD. Candidate > University of Southampton > > _______________________________________________ > Quantum ESPRESSO is supported by MaX > (https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.max-centre.eu%2F&data=01%7C01%7CG.A.Bramley%40soton.ac.uk%7Cff146e0c9f8442a6502408d86aaf85d0%7C4a5378f929f44d3ebe89669d03ada9d8%7C0&sdata=1iFjhj4tqm%2FF7Zmv5ob6KOGFn328kB6fdI5BpmoeUSY%3D&reserved=0) > users mailing list [email protected] > https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.quantum-espresso.org%2Fmailman%2Flistinfo%2Fusers&data=01%7C01%7CG.A.Bramley%40soton.ac.uk%7Cff146e0c9f8442a6502408d86aaf85d0%7C4a5378f929f44d3ebe89669d03ada9d8%7C0&sdata=Lv7plWOT%2B3hGuARAi%2BVgBKu51t94mxKdcmCP5J%2BIZug%3D&reserved=0 _______________________________________________ Quantum ESPRESSO is supported by MaX (https://eur03.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.max-centre.eu%2F&data=01%7C01%7CG.A.Bramley%40soton.ac.uk%7Cff146e0c9f8442a6502408d86aaf85d0%7C4a5378f929f44d3ebe89669d03ada9d8%7C0&sdata=1iFjhj4tqm%2FF7Zmv5ob6KOGFn328kB6fdI5BpmoeUSY%3D&reserved=0) users mailing list [email protected] https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.quantum-espresso.org%2Fmailman%2Flistinfo%2Fusers&data=01%7C01%7CG.A.Bramley%40soton.ac.uk%7Cff146e0c9f8442a6502408d86aaf85d0%7C4a5378f929f44d3ebe89669d03ada9d8%7C0&sdata=Lv7plWOT%2B3hGuARAi%2BVgBKu51t94mxKdcmCP5J%2BIZug%3D&reserved=0
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
