# Rotation Entropy for non-Abelian point group sym and CC-methods.

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 8:24:18 AM PDT - Mon, Mar 16th 2015 Hi. Rotation entropy of molecule depends on its pont group and symmetry number thereof, as described http://cccbdb.nist.gov/thermo.asp (eq 19), but when using CC-methods only abelian point groups is allowed. In the case of highly symmetric compounds such as cubane or dodecahedrane incorrect values of rotation entropy are obtained.

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 8:15:18 PM PDT - Wed, Mar 18th 2015 reusing existing hessian with proper symmetry group solve the problem.

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 11:34:18 PM PDT - Wed, Mar 18th 2015 Hi Vladimir, I am glad that you were able to solve this problem. Could you post an example input file demonstrating your solution? I will want to perform similar calculations in the future. Thanks, Matt

 9:00:38 AM PDT - Thu, Mar 19th 2015 Quote:Mernst Mar 19th 1:34 pmHi Vladimir, I am glad that you were able to solve this problem. Could you post an example input file demonstrating your solution? I will want to perform similar calculations in the future. Thanks, Matt Hi Matt, here is an example. As described in http://www.nwchem-sw.org/index.php/Vibration I reuse the previously computed hessian by specifying "reuse" in the "freq" module input block. ```title "N8-cubane CCSD/cc-pVDZ hessian" memory stack 100 mb heap 100 mb global 100 mb geometry symmetry Oh N 0.76104280 0.76104280 0.76104278 N -0.76104280 -0.76104280 0.76104278 N -0.76104280 0.76104280 -0.76104278 N 0.76104280 -0.76104280 -0.76104278 N -0.76104280 -0.76104280 -0.76104278 N 0.76104280 0.76104280 -0.76104278 N 0.76104280 -0.76104280 0.76104278 N -0.76104280 0.76104280 0.76104278 end freq reuse N8.hess end task tce freq ``` It is important that the order of the atoms during the calculation of hessian and its subsequent reusing were exactly the same. Check it out in the output file.