Default rsolv value in nwchem 6.3 vs earlier versions


Gets Around
On
http://nwchemgit.github.io/index.php/COSMO
which hasn't been updated since 2011, it says that
[rsolv   <real rsolv default 0.00>]

and later in the page it says
Quote:

"Rsolv" is a parameter used to define the solvent accessible surface. See the original reference of Klamt and Schuurmann for a description. The default value is 0.00 (in angstroms).


However, brief testing indicates that while this was true in e.g. nwchem 6.1 and 6.1.1 (and presumably earlier versions) in nwchem 6.3. the default is now 0.5 Ångström.

Is this just a case of the manual lagging behind?

There's nothing about the changed default on http://nwchemgit.github.io/index.php/NWChem_6.2 and I can't find any release notes in the sources.

Forum Regular
Hi, Thanks for catching that. We need to update the manual.

Best,
-Niri
niri.govind@pnl.gov

Forum Regular
Hi Ohlincha,

As part of the provision for analytical gradients in COSMO there were a couple of additional changes that fixed problems related to geometry optimizations:
1. The sum of COSMO charges formally should equal the total charge in the cavity. Previously the COSMO charges were "corrected" to force this relationship to hold. However, doing that violated the variational nature of the total energy resulting in incorrect gradients. Therefore this "correction" has been removed.
2. In geometry optimizations problems arise when a pair of COSMO charges get very close. This leads to inaccurate gradients and strange steps in the geometry optimizations. Setting Rsolv to 0.5 screens away COSMO charges that are closer together than 0.5 Angstrom and eliminates this problem.
So you are right that rsolv has a new default in the NWChem-6.3. This has been updated the documentation for NWChem-6.3 at http://nwchemgit.github.io/index.php/Release62:COSMO_Solvation_Model as far as I can see. Please let me know if you find an occurance that I have missed.

I hope this resolves any confusion about this issue.

Best wishes,

Huub

Gets Around
Niri and Huub,
thank you for your prompt replies and for confirming the change.
Andy


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