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State	Conformation	minimum conformation	conformer description	state description
1	1	no	D*H	¹Σ_g
1	2	yes	C2H	¹A_G

	hartrees
Energy at 0K	-152.820122
Energy at 298.15K
HF Energy	-152.443007
Nuclear repulsion energy	75.871738

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	Σ_g	3442	3302	0.00
2	Σ_g	2266	2174	0.00
3	Σ_g	877	841	0.00
4	Σ_u	3442	3302	94.87
5	Σ_u	2057	1974	0.04
6	Π_g	569	546	0.00
6	Π_g	569	546	0.00
7	Π_g	804i	772i	0.00
7	Π_g	804i	772i	0.00
8	Π_u	520	499	126.14
8	Π_u	520	499	126.14
9	Π_u	130	125	0.12
9	Π_u	130	125	0.12

Atom	x (Å)	y (Å)	z (Å)
C1	0.000	0.000	0.699
C2	0.000	0.000	-0.699
C3	0.000	0.000	1.927
C4	0.000	0.000	-1.927
H5	0.000	0.000	3.000
H6	0.000	0.000	-3.000

	C1	C2	C3	C4	H5	H6
C1		1.3990	1.2277	2.6266	2.3007	3.6996
C2	1.3990		2.6266	1.2277	3.6996	2.3007
C3	1.2277	2.6266		3.8543	1.0730	4.9273
C4	2.6266	1.2277	3.8543		4.9273	1.0730
H5	2.3007	3.6996	1.0730	4.9273		6.0003
H6	3.6996	2.3007	4.9273	1.0730	6.0003

All results from a given calculation for C₄H₂ (Diacetylene)

using model chemistry: CCD/6-31G

States and conformations

Conformer 1 (D*H)

Conformer 2 (C2H)

	Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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	hartrees
Energy at 0K	-152.820645
Energy at 298.15K	-152.819560
HF Energy	-152.441855
Nuclear repulsion energy	75.892554

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3447	3307	0.00
2	A_g	2268	2176	0.00
3	A_g	883	847	0.00
4	A_g	761	730	0.00
5	A_g	583	559	0.00
6	A_u	599	575	115.39
7	A_u	187	179	2.50
8	B_g	610	586	0.00
9	B_u	3447	3307	92.59
10	B_u	2061	1978	0.03
11	B_u	671	644	107.63
12	B_u	210	202	6.43

Atom	x (Å)	y (Å)
C1	-0.030	0.699
C2	0.030	-0.699
C3	0.030	1.925
C4	-0.030	-1.925
H5	0.011	2.998
H6	-0.011	-2.998

	C1	C2	C3	C4	H5	H6
C1		1.3985	1.2281	2.6239	2.2994	3.6964
C2	1.3985		2.6239	1.2281	3.6964	2.2994
C3	1.2281	2.6239		3.8510	1.0726	4.9231
C4	2.6239	1.2281	3.8510		4.9231	1.0726
H5	2.2994	3.6964	1.0726	4.9231		5.9954
H6	3.6964	2.2994	4.9231	1.0726	5.9954

atom1	atom2	atom3	angle		atom1	atom2	atom3	angle
C1	C2	C4	180.000		C1	C3	H5	180.000
C2	C1	C3	180.000		C2	C4	H6	180.000

atom1	atom2	atom3	angle		atom1	atom2	atom3	angle
C1	C2	C4	174.803		C1	C3	H5	176.262
C2	C1	C3	174.803		C2	C4	H6	176.262

All results from a given calculation for C4H2 (Diacetylene)

using model chemistry: CCD/6-31G

States and conformations

Conformer 1 (D*H)

Conformer 2 (C2H)

All results from a given calculation for C₄H₂ (Diacetylene)