GreenGroup/RMG-Java — comment on commit 52a77b56fe4afde5732719e3c38893080be0bd9f
File:  line 0
By gmagoon:

This also works for fulvene and cyclopentadienyl (no B bonds) but fails for cycC5H4...I'll have to do some further tweaking, perhaps using Nick's fix for Cdd types:

C5H4
1 C 0 {2,S} {5,D}
2 C 0 {1,S} {3,D}
3 C 0 {2,D} {4,S}
4 C 0 {3,S} {5,D}
5 C 0 {4,D} {1,D}

Created new species: C5H4(3)
ChemFormula: C5H5
1 C 0 {2,B} {5,B} {6,S}
2 C 0 {1,B} {3,B} {7,S}
3 C 0 {2,B} {4,B} {8,S}
4 C 0 {3,B} {5,B} {9,S}
5 C 0 {4,B} {1,B} {10,S}
6 H 0 {1,S}
7 H 0 {2,S}
8 H 0 {3,S}
9 H 0 {4,S}
10 H 0 {5,S}

The number of resonance isomers is 0
The NASA data is
!Estimated by RMG using Group Additivity
!Group:Cb-H Group:Cb-H Group:Cb-H Group:Cb-H Group:Cb-H Ring:Ring
C5H4(3) C 5H 5 G 250.000 5000.000 995.043 1
1.01842412E+01 1.54822721E-02-5.07870826E-06 7.63827086E-10-4.33737429E-14 2
3.10813200E+03-3.92308439E+01 3.33841259E+00-6.03950885E-03 1.01293549E-04 3
-1.20035679E-07 4.27514903E-11 6.89833559E+03 5.96190292E+00 4

ThermoData is
16.5 53.07 16.2 22.2 27.3 31.5 37.7 42.05 48.65
symmetry number = 10
C5H5 H = 16.5