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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	-153.027724
Energy at 298.15K
HF Energy	-152.505294
Nuclear repulsion energy	75.755219

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	Σ_g	3477	3334	0.00
2	Σ_g	2174	2085	0.00
3	Σ_g	895	858	0.00
4	Σ_u	3477	3334	166.14
5	Σ_u	1981	1899	1.24
6	Π_g	551	529	0.00
6	Π_g	551	529	0.00
7	Π_g	653i	626i	0.00
7	Π_g	653i	626i	0.00
8	Π_u	508	488	86.81
8	Π_u	508	488	86.81
9	Π_u	151	145	2.07
9	Π_u	151	145	2.07

Atom	x (Å)	y (Å)	z (Å)
C1	0.000	0.000	0.691
C2	0.000	0.000	-0.691
C3	0.000	0.000	1.930
C4	0.000	0.000	-1.930
H5	0.000	0.000	3.005
H6	0.000	0.000	-3.005

	C1	C2	C3	C4	H5	H6
C1		1.3825	1.2387	2.6213	2.3133	3.6959
C2	1.3825		2.6213	1.2387	3.6959	2.3133
C3	1.2387	2.6213		3.8600	1.0746	4.9346
C4	2.6213	1.2387	3.8600		4.9346	1.0746
H5	2.3133	3.6959	1.0746	4.9346		6.0092
H6	3.6959	2.3133	4.9346	1.0746	6.0092

All results from a given calculation for C₄H₂ (Diacetylene)

using model chemistry: MP2/aug-cc-pVDZ

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	-153.027944
Energy at 298.15K	-153.026705
HF Energy	-152.504884
Nuclear repulsion energy	75.763272

Atom	x (Å)	y (Å)
C1	-0.023	0.691
C2	0.023	-0.691
C3	0.023	1.929
C4	-0.023	-1.929
H5	-0.002	3.003
H6	0.002	-3.003

	C1	C2	C3	C4	H5	H6
C1		1.3823	1.2390	2.6197	2.3126	3.6942
C2	1.3823		2.6197	1.2390	3.6942	2.3126
C3	1.2390	2.6197		3.8582	1.0746	4.9323
C4	2.6197	1.2390	3.8582		4.9323	1.0746
H5	2.3126	3.6942	1.0746	4.9323		6.0066
H6	3.6942	2.3126	4.9323	1.0746	6.0066

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

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3477	3334	0.00
2	A_g	2173	2084	0.00
3	A_g	897	861	0.00
4	A_g	616	590	0.00
5	A_g	555	532	0.00
6	A_u	556	533	83.73
7	A_u	188	180	4.70
8	B_g	574	550	0.00
9	B_u	3477	3334	165.26
10	B_u	1980	1898	1.28
11	B_u	595	571	83.12
12	B_u	207	199	6.93

atom1	atom2	atom3	angle		atom1	atom2	atom3	angle
C1	C2	C4	176.007		C1	C3	H5	176.596
C2	C1	C3	176.007		C2	C4	H6	176.596

All results from a given calculation for C4H2 (Diacetylene)

using model chemistry: MP2/aug-cc-pVDZ

States and conformations

Conformer 1 (D*H)

Conformer 2 (C2H)

All results from a given calculation for C₄H₂ (Diacetylene)