CCL: [EXTERNAL] CCL:G: Adding many explicit water molecules to the model

["Close, David M." <CLOSED[#]mail.etsu.edu>]

 Sent to CCL by: "Close, David M." [CLOSED===mail.etsu.edu]
 Grigoriy:
   I have looked at your figure and see things that don't look right.  Your
 picture can't be rotated, so I can't see how far some of the bonds are apart.
 When you made this drawing did you go back to Chemcraft and try an optimization?
   Also I would try to use just a few waters and see how they respond.  Try just
 three of four waters and perform an optimization.  Then one at a time put in
 more waters, with each new water try an optimization.
 I bet that you can get the number of waters that you used, but they will be in
 different.
   Regards, Dave Close.
 -----Original Message-----
 > From: owner-chemistry+closed==etsu.edu..ccl.net
 <owner-chemistry+closed==etsu.edu..ccl.net> On Behalf Of Grigoriy Zhurko
 reg_zhurko_-_chemcraftprog.com
 Sent: Monday, December 19, 2022 4:16 AM
 To: Close, David M. <CLOSED..mail.etsu.edu>
 Subject: [EXTERNAL] CCL:G: Adding many explicit water molecules to the model
 I need to compute the pKa values of some carbon acids and phenols, and it is a
 common practice to add 1-3 explicit water molecules, bonded with polar groups of
 the studied molecule, to better take into account the specific solvation effects
 (in addition to CPCM model). I tried to add many water molecules (14) for better
 results - see attached picture. The results are interesting. At one side,
 possibly very big error is produced by the existence of many local minimums with
 different numbers of h bonds. How these minimums should be named in paper -
 maybe "conformations", "configurations", "geometrical
 configurations", "local minimums"?
 Then I found, that if the computation of different acids is performed with same
 geometrical configurations of 5 h2o molecules bound to -COOH, and with same
 configurations for neutral molecule and anion, possibly the results are quite
 good (a common correlation can be obtained for carbon acids and phenols). So I
 want to publish these results; but I need to read more works when this approach
 (adding many explicit water molecules) was used. Can you suggest such papers?
 By the way, using my program Chemcraft is important for such jobs, because the
 "Structures merger" utility in in allows one to transfer several H2O
 molecules in same configuration from one acid to another.
 Grigoriy Zhurk