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IV.A.4. (XIV.F.)

Relative enthalpies of isomers - Comparison of 298.15K enthalpies (kJ mol-1)

Isomers of C8H6

index Species CAS number Name Relative experimental enthalpy (kJ mol-1) sketch
a C8H6 250259 Pentalene   sketch of Pentalene
b C8H6 4026237 benzocyclobutadiene   sketch of benzocyclobutadiene
c C8H6 6249236 Calicene   sketch of Calicene
d C6H5CCH 536743 phenylacetylene 0.0 sketch of phenylacetylene
The calculated enthalpies include the calculated and scaled vibrational zero-point energy.
Methods with predefined basis sets
semi-empirical AM1 411.4 a
157.3 b
568.1 c
0.0 d
PM3 84.8 a
121.6 b
234.9 c
0.0 d
PM6 48.2 a
59.3 b
171.3 c
0.0 d
composite G1 -557.3 a
-522.8 b
-410.2 c
0.0 d
G2MP2 -561.9 a
-527.3 b
-415.1 c
0.0 d
G2 -562.8 a
-528.5 b
-416.8 c
0.0 d
G3 -557.3 a
-523.2 b
-411.0 c
0.0 d
G3B3 59.9 a
95.2 b
208.4 c
0.0 d
G3MP2
0.0 d
G4
205.6 c
0.0 d
CBS-Q NC
NC
NC

Methods with standard basis sets
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) 6-311+G(3df,2p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ cc-pV(T+d)Z
hartree fock HF
0.0 d

0.0 d

0.0 d

0.0 d
 
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
density functional LSDA
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
 
0.0 d

0.0 d

0.0 d
 
0.0 d
BLYP
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
     
0.0 d

0.0 d
   
0.0 d
B1B95
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
 
0.0 d

0.0 d

0.0 d
 
0.0 d
B3LYP
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
 
0.0 d

0.0 d

0.0 d
 
0.0 d
B3PW91
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
     
0.0 d

0.0 d
   
0.0 d
mPW1PW91
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
     
0.0 d

0.0 d
   
0.0 d
PBEPBE
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
 
0.0 d

0.0 d
   
0.0 d
PBEPBEultrafine        
0.0 d
                     
Moller Plesset perturbation MP2
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
 
0.0 d
     
0.0 d
MP2=FULL
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
     
0.0 d
       
Configuration interaction CID  
0.0 d
   
0.0 d
                     
CISD  
0.0 d
   
0.0 d
                     
Quadratic configuration interaction QCISD
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
         
0.0 d
       
Coupled Cluster CCD  
0.0 d
   
0.0 d

0.0 d
                   

Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
density functional B1B95
0.0 d

0.0 d
       
B3LYP
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
Moller Plesset perturbation MP2
0.0 d

0.0 d

0.0 d

0.0 d

0.0 d

0.0 d
NC = not calculated
For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.
gaw refers to the group additivity method implemeted in the NIST Chemistry Webbook.

See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.