Multipole Correction for Adsorption Energies of Charged Molecules
Posted: Mon Jun 08, 2020 11:11 am
Hi all,
I have been doing adsorption energy calculations of charged (using NELECT, so charged super cell) isolated smaller molecules on larger molecules and have found the quadrupole corrections to be exceptionally large (approx. 30 eV) when adding two excess electrons to the system. I have confirmed using charge density difference plots that the charge from the extra electron remains localised.
I realise VASP has the limitation that for charged systems quadrupole corrections are only correct for cubic super cells. Because my system consists of isolated molecules a cubic supercell cannot be used (must be orthorhombic).
Based on the VASP wiki is it best just to set the LDIPOL tag and leave out the IDIPOL and LMONO tags in the INCAR file, as it seems VASP automatically determines if the system is charged?
The alternative might be to turn off the multipole correction/s which seems to provide adsorptions energies closer to what I’d expect but I’m not sure this would be good practice as we want to reduce interactions/contributions between period supercells.
I realise this question has been asked before (see below links). I just want to make sure I’m interpreting the wiki recommendations correctly as the answers provided by the admin just referred onto the manual/wiki. However, the Admin does recommend that multipole corrections be included.
forum/viewtopic.php?f=4&t=1827&p=1872&h ... cule#p1872
Other links to forum posts on corrections for charged systems:
forum/viewtopic.php?f=4&t=17138&p=17753 ... ule#p17753
forum/viewtopic.php?f=4&t=17117&p=17683 ... 539#p17683
Kind regards,
Ollie
I have been doing adsorption energy calculations of charged (using NELECT, so charged super cell) isolated smaller molecules on larger molecules and have found the quadrupole corrections to be exceptionally large (approx. 30 eV) when adding two excess electrons to the system. I have confirmed using charge density difference plots that the charge from the extra electron remains localised.
I realise VASP has the limitation that for charged systems quadrupole corrections are only correct for cubic super cells. Because my system consists of isolated molecules a cubic supercell cannot be used (must be orthorhombic).
Based on the VASP wiki is it best just to set the LDIPOL tag and leave out the IDIPOL and LMONO tags in the INCAR file, as it seems VASP automatically determines if the system is charged?
The alternative might be to turn off the multipole correction/s which seems to provide adsorptions energies closer to what I’d expect but I’m not sure this would be good practice as we want to reduce interactions/contributions between period supercells.
I realise this question has been asked before (see below links). I just want to make sure I’m interpreting the wiki recommendations correctly as the answers provided by the admin just referred onto the manual/wiki. However, the Admin does recommend that multipole corrections be included.
forum/viewtopic.php?f=4&t=1827&p=1872&h ... cule#p1872
Other links to forum posts on corrections for charged systems:
forum/viewtopic.php?f=4&t=17138&p=17753 ... ule#p17753
forum/viewtopic.php?f=4&t=17117&p=17683 ... 539#p17683
Kind regards,
Ollie