From NWChem
Viewed 3142 times, With a total of 4 Posts
|
|
|
Clicked A Few Times
Threads 2
Posts 7
|
|
| 2:08:28 PM PDT - Fri, May 10th 2013 |
|
Hello,
I am trying to calculate the delta G of a molecule and am having trouble figuring out what values I need to use to do so at a given temperature. I run a geometry optimization followed by a frequency calculation and I get this section in the output:
From the projected analysis
The Zero-Point Energy (Kcal/mol) = 28.51472262
center of mass
--------------
x = 0.00000163 y = 0.00000203 z = 0.00000051
moments of inertia (a.u.)
------------------
11.468747259680 0.000017667545 -0.000007476804
0.000017667545 11.468763189783 0.000011061644
-0.000007476804 0.000011061644 11.468783251860
Rotational Constants
--------------------
A= 5.249070 cm-1 ( 7.552071 K)
B= 5.249051 cm-1 ( 7.552045 K)
C= 5.249044 cm-1 ( 7.552035 K)
Temperature = 298.15K
frequency scaling parameter = 1.0000
Zero-Point correction to Energy = 28.493 kcal/mol ( 0.045406 au)
Thermal correction to Energy = 30.287 kcal/mol ( 0.048266 au)
Thermal correction to Enthalpy = 30.880 kcal/mol ( 0.049210 au)
Total Entropy = 49.384 cal/mol-K
- Translational = 34.246 cal/mol-K (mol. weight = 16.0313)
- Rotational = 15.068 cal/mol-K (symmetry # = 1)
- Vibrational = 0.070 cal/mol-K
Cv (constant volume heat capacity) = 6.384 cal/mol-K
- Translational = 2.979 cal/mol-K
- Rotational = 2.979 cal/mol-K
- Vibrational = 0.425 cal/mol-K
What values do I need to use in my calculation? Is the thermal correction to Enthalpy the Enthalpy or do I need to add/subtract it from something?
Thank you in advance.
|
|
|
-
Bert Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop
|
|
|
Forum Vet
Threads 4
Posts 597
|
|
| 2:15:20 PM PDT - Mon, May 13th 2013 |
|
| The thermal correction to enthalpy should get you to Delta H. To get to Delta G you need Delta H - T Delta S
|
|
|
|
|
|
Clicked A Few Times
Threads 2
Posts 7
|
|
| 3:29:35 PM PDT - Mon, May 13th 2013 |
|
| So then my Delta G with the posted data is 30.880 - T* 49.384? I just want to make sure I am using the right values.
|
|
|
|
|
|
Clicked A Few Times
Threads 11
Posts 32
|
|
| 3:45:08 PM PDT - Mon, May 13th 2013 |
|
Quote:Beckmw May 13th 3:29 pmSo then my Delta G with the posted data is 30.880 - T* 49.384? I just want to make sure I am using the right values.
yes but make sure you are using the same energy units!! deltaH is kcal/mol, and deltaS is cal/mol.K
|
|
|
|
|
|
Clicked A Few Times
Threads 2
Posts 7
|
|
| 3:46:24 PM PDT - Mon, May 13th 2013 |
|
Quote:DouDou May 13th 3:45 pmQuote:Beckmw May 13th 3:29 pmSo then my Delta G with the posted data is 30.880 - T* 49.384? I just want to make sure I am using the right values.
yes but make sure you are using the same energy units!! deltaH is kcal/mol, and deltaS is cal/mol.K
Oh wow good catch! Thank you!
|
|
|
AWC's:
2.5.10 MediaWiki - Stand Alone Forum Extension
Forum theme style by: AWC
