CCL: questions on convergence, restarting jobs, counterpoise



 Sent to CCL by: "Saurabh S Chitnis" [sschitnis _ gmail.com]
 Hello,
 I have three questions:
 1. In many of my "opt" and "freq=raman" jobs, I find that
 the calculation completes successfully with
 the forces having converged but the displacements still being above the
 convergence threshold. How
 can this be fixed? I usually face this problem when using opt=verytight and
 int=ultrafine.
 2. Is there any way of restarting an analytic frequency job which has completed
 but not converged?
 3. Can the output of a counterpoise calculation (i.e. the Corrected total
 energy) be interpreted as a
 bond-dissociation energy between the two fragments?
 Here are some details regarding the above questions:
 theory: DFT (B3LYP, PBE1PBE and B3PW91)
 basis-set: cc-pvtz and aug-cc-pvtz
 systems being calcualated: P2Me4, [P2Me5]+ and [P2Me6]2+
 for the couterpoise: I'm trying to get the P-P bond dissocation energy. So I
 optimize the geometry as
 per usual and then redefine the optimized P2Me4 as fragment1(Me2P) and
 fragment2(PMe2) to run
 the counterpoise calculation. The result should be the homolytic bond
 dissociation energy right?
 cheers
 Saurabh