18 September 2012

240. Harmonic frequency scaling in NWChem

...is difficult to find information about, but apparently it IS possible:
http://www.emsl.pnl.gov/docs/nwchem/nwchem-support/2012/08/0021._NWCHEM_FW:_BOUNCE_nwchem-users_emsl.pnl

Example input:

Title "acetate"

Start  acetate

echo

charge -1

geometry autosym units angstrom
 C     0.0191498     0.0215213     0.0191498
 H     -0.621688     -0.620669     0.658428
 H     0.658428     -0.620669     -0.621688
 H     -0.628475     0.649316     -0.628475
 C     0.881900     0.883055     0.881900
 O     1.74905     0.315740     1.74905
 O     0.799516     2.22959     0.799516
end

basis
* library "cc-pvtz"
end

dft
  mult 1
  direct
  noio
  XC b3lyp
  grid fine
  mulliken
end

driver
end

set vib:scalefreq  0.9854

task dft optimize
task dft freq

which gives:

 Temperature                      =   298.15K
 frequency scaling parameter      =   0.9854

 Zero-Point correction to Energy  =   29.486 kcal/mol  (  0.046990 au)
 Thermal correction to Energy     =   31.752 kcal/mol  (  0.050601 au)
 Thermal correction to Enthalpy   =   32.345 kcal/mol  (  0.051544 au)

 Total Entropy                    =   64.086 cal/mol-K
   - Translational                =   38.129 cal/mol-K (mol. weight =  59.0133)
   - Rotational                   =   23.739 cal/mol-K (symmetry #  =        1)
   - Vibrational                  =    2.218 cal/mol-K

 Cv (constant volume heat capacity) =   11.268 cal/mol-K
   - Translational                  =    2.979 cal/mol-K
   - Rotational                     =    2.979 cal/mol-K
   - Vibrational                    =    5.309 cal/mol-K

c.f.

 Temperature                      =   298.15K
 frequency scaling parameter      =   1.0000

 Zero-Point correction to Energy  =   29.923 kcal/mol  (  0.047686 au)
 Thermal correction to Energy     =   32.173 kcal/mol  (  0.051272 au)
 Thermal correction to Enthalpy   =   32.766 kcal/mol  (  0.052215 au)

 Total Entropy                    =   64.008 cal/mol-K
   - Translational                =   38.129 cal/mol-K (mol. weight =  59.0133)
   - Rotational                   =   23.739 cal/mol-K (symmetry #  =        1)
   - Vibrational                  =    2.141 cal/mol-K

 Cv (constant volume heat capacity) =   11.132 cal/mol-K
   - Translational                  =    2.979 cal/mol-K
   - Rotational                     =    2.979 cal/mol-K
   - Vibrational                    =    5.173 cal/mol-K

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