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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	-152.807182
Energy at 298.15K
HF Energy	-152.440646
Nuclear repulsion energy	75.710116

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	Σ_g	3475	3325	0.00
2	Σ_g	2196	2101	0.00
3	Σ_g	877	839	0.00
4	Σ_u	3475	3325	114.00
5	Σ_u	1977	1892	0.04
6	Π_g	547	523	0.00
6	Π_g	547	523	0.00
7	Π_g	885i	847i	0.00
7	Π_g	885i	847i	0.00
8	Π_u	456	436	128.87
8	Π_u	456	436	128.87
9	Π_u	95	91	0.69
9	Π_u	95	91	0.69

Atom	x (Å)	y (Å)	z (Å)
C1	0.000	0.000	0.695
C2	0.000	0.000	-0.695
C3	0.000	0.000	1.932
C4	0.000	0.000	-1.932
H5	0.000	0.000	3.002
H6	0.000	0.000	-3.002

	C1	C2	C3	C4	H5	H6
C1		1.3900	1.2372	2.6273	2.3074	3.6974
C2	1.3900		2.6273	1.2372	3.6974	2.3074
C3	1.2372	2.6273		3.8645	1.0702	4.9347
C4	2.6273	1.2372	3.8645		4.9347	1.0702
H5	2.3074	3.6974	1.0702	4.9347		6.0048
H6	3.6974	2.3074	4.9347	1.0702	6.0048

All results from a given calculation for C₄H₂ (Diacetylene)

using model chemistry: MP2/6-31G

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	-152.807870
Energy at 298.15K	-152.806737
HF Energy	-152.439178
Nuclear repulsion energy	75.723509

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3479	3329	0.00
2	A_g	2196	2101	0.00
3	A_g	883	845	0.00
4	A_g	755	723	0.00
5	A_g	590	565	0.00
6	A_u	555	531	119.53
7	A_u	181	173	1.17
8	B_g	589	564	0.00
9	B_u	3479	3328	111.79
10	B_u	1980	1894	0.05
11	B_u	652	623	112.55
12	B_u	217	208	6.37

Atom	x (Å)	y (Å)
C1	-0.032	0.694
C2	0.032	-0.694
C3	0.032	1.930
C4	-0.032	-1.930
H5	0.006	3.000
H6	-0.006	-3.000

	C1	C2	C3	C4	H5	H6
C1		1.3895	1.2380	2.6244	2.3061	3.6940
C2	1.3895		2.6244	1.2380	3.6940	2.3061
C3	1.2380	2.6244		3.8612	1.0698	4.9303
C4	2.6244	1.2380	3.8612		4.9303	1.0698
H5	2.3061	3.6940	1.0698	4.9303		5.9997
H6	3.6940	2.3061	4.9303	1.0698	5.9997

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	174.415		C1	C3	H5	175.649
C2	C1	C3	174.415		C2	C4	H6	175.649

All results from a given calculation for C4H2 (Diacetylene)

using model chemistry: MP2/6-31G

States and conformations

Conformer 1 (D*H)

Conformer 2 (C2H)

All results from a given calculation for C₄H₂ (Diacetylene)