Accuracy of Prediction of Heat Capacity (Home)

Back to features of PM6

The heat capacity, Cp, of gas-phase systems can be predicted using the calculated vibrational frequencies and moments of inertia and the translational contributions. For monatomic species, only translational contributions were used. The heat capacity at constant volume, Cv, can be derived from Cv = Cp - R, where R=1.987 calories. All reference data is taken from the Handbook of Chemistry and Physics.

 

Statistics for the set of 121 species

Average signed error:

  0.75 0.37*

Average unsigned error: 

  1.48 1.12*

Root mean square error:

  3.14 1.64*

*: Excluding the worst three results

Each of the PM6 results given below was generated by doing two calculations.  First, the geometry was optimized, then a THERMO calculation was done.  These calculations were done in a single run, with the data set having the form:

<keywords: none used>
<Name of species>
<Blank>
<Z-matrix: For examples, see: ref-data>
<Blank line>
 OLDGEO THERMO(298,298,0)
<Blank line>
<Blank line>

 

 

Heat Capacities for Individual Species used in Preparing this Graph
(All values are in cal/(degree.mole))

Formula

Molecule

Exp. PM6. Diff

B5H9

Pentaborane(9)

23.80

28.76

-4.96

B5H11

Pentaborane(11)

31.14

28.76

2.38

C2H2

Acetylene

10.52

8.94

1.58

C3H6

Cyclopropane

13.29

13.10

0.19

C3H8

Propane

17.59

17.34

0.25

BC3H9

Trimethylborane

21.15

24.73

-3.58

C6H6

Benzene

19.69

19.45

0.24

C10H8

Naphthalene

31.52

30.96

0.56

CNH5

Methylamine

11.97

11.49

0.48

C2NH3

Acetonitrile

12.48

12.11

0.37

C2NH7

Dimethylamine

16.90

15.98

0.92

C2NH7

Ethylamine

17.09

14.56

2.53

C3NH9

Trimethylamine

21.94

21.45

0.49

C6NH7

Aniline

25.79

24.75

1.04

C7NH9

m-Toluidine

30.00

29.39

0.61

C7NH9

o-Toluidine

31.11

29.20

1.91

C7NH9

p-Toluidine

30.16

28.89

1.27

C2N2

Cyanogen

13.58

12.15

1.43

CH2O

Formaldehyde

8.46

8.62

-0.16

CH4O

Methanol

10.54

11.10

-0.56

C2H2O

Ketene

12.38

11.82

0.56

C2H6O

Dimethyl ether

15.39

15.91

-0.52

C2H6O

Ethanol

15.68

16.24

-0.56

C3H6O

Acetone

17.81

18.68

-0.87

C3H6O

Propanal

19.29

17.86

1.43

C3H8O

Isopropanol

21.34

21.71

-0.37

C3H8O

Propanol

20.46

19.06

1.40

C4H4O

Furan

15.63

15.71

-0.08

C4H6O

2,3-Dihydrofuran

19.07

17.85

1.22

C2H2O2

trans Glyoxal

14.48

14.37

0.11

C2H4O2

Acetic acid

15.15

16.83

-1.68

C2H6O2

Ethylene glycol

19.77

16.70

3.07

C3H6O2

Methyl acetate

20.55

18.57

1.98

CNH3O2

Nitromethane

13.26

14.66

-1.40

C2NH5O2

Nitroethane

18.88

17.46

1.42

C6NH5O2

Nitrobenzene

28.78

27.74

1.04

CNH3O3

Methyl nitrate

18.31

17.66

0.65

C3NH7O3

Propyl nitrate

29.44

24.27

5.17

CN2H2O4

Dinitromethane

20.65

21.82

-1.17

CN4O8

Tetranitromethane

42.09

34.69

7.40

C3N3H5O9

Glycerol trinitrate

55.98

37.05

18.93

C5N4H8O12

Pentaerythritol tetranitrate

70.45

49.03

21.42

F

Fluorine, atom

5.42

4.97

0.45

CH3F

Fluoromethane

8.96

9.17

-0.21

C2HF

Fluoroacetylene

12.52

11.22

1.30

C2H5F

Fluoroethane

14.00

13.81

0.19

CNF

Cyanogen fluoride

9.99

9.33

0.66

F2

Fluorine

7.45

7.44

0.01

OF2

Difluorine oxide

10.35

9.77

0.58

COF2

Carbonyl fluoride

11.19

11.89

-0.70

C2H3F3

1,1,1-Trifluoroethane

18.69

18.62

0.07

NF3

Nitrogen trifluoride

12.76

12.58

0.18

C2NF3

Trifluoroacetonitrile

18.62

18.57

0.05

CF4

Carbon tetrafluoride

14.60

15.50

-0.90

C2F6

Hexafluoroethane

25.50

23.95

1.55

NaF

Sodium fluoride

7.65

8.10

-0.45

SiCH6

Methylsilane

16.99

16.27

0.72

SiC3H10

Trimethylsilane

28.18

29.01

-0.83

SiC4H12

Tetramethylsilane

34.39

36.96

-2.57

Si2C6H18O

Hexamethyldisiloxane

57.00

55.67

1.33

PF3

Phosphorus trifluoride

14.02

14.79

-0.77

POF3

Phosphorus oxyfluoride

16.44

18.14

-1.70

CH4S

Thiomethanol

12.02

12.05

-0.03

C2H6S

Thioethanol

17.71

16.90

0.81

C3H6S

Thietane

16.32

16.48

-0.16

C4H10S

Diethyl thioether

27.96

23.71

4.25

C2H6SO2

Dimethyl sulfone

23.90

23.99

-0.09

SO2F2

Sulfuryl fluoride

15.77

18.00

-2.23

CH3Cl

Methyl chloride

9.75

9.89

-0.14

C2HCl

Chloroacetylene

12.98

11.59

1.39

C2H5Cl

Chloroethane

15.01

14.60

0.41

CNCl

Cyanogen chloride

10.75

10.24

0.51

ClF

Chlorine fluoride

7.67

10.24

-2.57

ClF3

Chlorine trifluoride

15.27

15.66

-0.39

Cl2

Chlorine

8.10

8.03

0.07

CH2Cl2

Dichloromethane

12.19

12.27

-0.08

CCl2O

Carbonyl chloride

13.79

13.70

0.09

SCl2O2

Sulfuryl chloride

18.40

19.21

-0.81

BCl3

Boron trichloride

14.99

19.21

-4.22

C2H3Cl3

1,1,1-Trichloroethane

22.30

21.81

0.49

SiHCl3

Trichlorosilane

18.12

18.60

-0.48

PCl3

Phosphorus trichloride

17.16

17.31

-0.15

PCl3O

Phosphorus oxychloride

20.29

20.96

-0.67

SiCl4

Silicon tetrachloride

21.58

22.12

-0.54

PCl5

Phosphorus pentachloride

26.96

23.58

3.38

Ar

Argon, atom

4.97

4.97

0.00

TiCl4

Titanium tetrachloride

22.80

19.87

2.93

CrO3

Chromium(VI) trioxide

13.38

14.39

-1.01

CrCl2O2

Chromium dioxide dichloride

20.20

21.10

-0.90

GeH3F

Fluorogermane

11.33

13.02

-1.69

GeCl4

Germanium tetrachloride

22.97

23.48

-0.51

AsH3

Arsine

9.11

9.03

0.08

AsF3

Arsenic trifluoride

15.68

16.23

-0.55

AsCl3

Arsenic trichloride

18.09

18.12

-0.03

HBr

Hydrogen bromide

6.96

6.96

0.00

CH3Br

Bromomethane

10.13

10.41

-0.28

C2HBr

Bromoacetylene

13.31

11.91

1.40

C2H5Br

Bromoethane

15.42

15.09

0.33

CNBr

Cyanogen bromide

11.21

10.79

0.42

NBrO

Nitrosyl bromide

10.87

10.05

0.82

BrF

Bromine fluoride

7.89

7.71

0.18

BrF3

Bromine trifluoride

15.92

16.20

-0.28

BrF5

Bromine pentafluoride

23.80

22.23

1.57

SiH3Br

Bromosilane

12.62

13.15

-0.53

BrCl

Bromine chloride

8.37

8.32

0.05

GeH3Br

Bromogermane

13.48

14.11

-0.63

Br2

Bromine

8.60

8.59

0.01

CBr2F2

Difluorodibromomethane

18.40

18.56

-0.16

SiHBr3

Tribromosilane

19.31

19.84

-0.53

AsBr3

Arsenic tribromide

18.93

15.08

3.85

NbCl5

Niobium(V) pentachloride

28.87

24.61

4.26

MoF6

Molybdenum(VI) hexafluoride

28.82

24.94

3.88

SnCl4

Tin tetrachloride

23.49

19.89

3.60

CH3I

Methyl iodide

10.54

10.95

-0.41

C2H5I

Iodoethane

15.99

15.53

0.46

CIF3

Trifluoroiodomethane

16.95

17.35

-0.40

IBr

Iodine bromide

8.70

8.75

-0.05

C2I2

Diiodoacetylene

16.80

15.99

0.81

BI3

Boron triiodide

16.92

13.05

3.87

CsHO

Cesium hydroxide

11.88

11.33

0.55

WF6

Tungsten hexafluoride

28.44

25.55

2.89

BiCl3

Bismuth trichloride

19.05

14.91

4.14