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Re^2: Mixing basis sets

Stefan Boresch

Thank you for the info, best regards,


On Wed Apr 21 '10 3:41pm, Evgeniy wrote
>Dear Stefan Boresch

>For your purposes You can do scanning with help of DLC engine which is implemented in Firefly, please refer to built-in Firefly manual. Some DLC options not included in manual can be found:

>Generally, You should add the following strings to your input file:

>$CONTRL NZVAR=x $END where x = 3n-6, n - number of atoms in your molecule

>and specify by IFZMAT(1) keyword an arrange of atoms that corresponds to:
>1. an internal coordinate you want to scan along
>2. an internal coordinate you want to freeze

>For example, IFZMAT(1)=1,2,3, 3,5,6,8,18 means that you scan along the 2,3 atom pair bond length and freeze dihedral angle between 5,6 and 8,18 atom pairs. Also You must input $SURF group with it's related keywords to specify your surface scanning options.
>With such input options You can use cartesian coordinates during scanning and set different basis set for each atom in the manner convenient for You.

>On Wed Apr 21 '10 10:03am, Stefan Boresch wrote
>>We plan to scan energy surfaces of N-acetyl-methylamide amino
>>acids ("blocked" amino acids) to verify (or disprove) "features" found in various force fields. In the case of, e.g.,  Ser, this is a 23 atom / 86 electron system. At both ends of these systems, there are methyl groups that are almost certainly devoid of any interest; however, they cannot be replaced by a hydrogen. Since eventually we may need multiple geometry optimizations on the MP2 level, I would like to use a minimal basis set for these, and a reasonable basis for the interesting part of the molecule.

>>Now, if I set COORD=UNIQUE, then this is easy and well documented and
>>the PUNCH file is my friend... However, in the scans of the energy surface I need dihedral angles frozen. This seems to imply using
>>COORD=ZMT (or ZMTMPC). Is there a way to supply explicitly a basis set
>>for each atom when using/relying on coordinates in z-matrix format?

>>Alternatively, is there a way to freeze certain degrees of freedom
>>if cartesian (unique) coordinates are used?

>>Apologies if I overlook something trivial in the documentation; as
>>far as quantum chemical calculations are concerned, I am a complete
>>beginner ...

>>Thanks for any hints,

>>Stefan Boresch

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