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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	-152.011915
Energy at 298.15K
HF Energy	-151.648127
Nuclear repulsion energy	76.261099

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	Σ_g	3473	3315	0.00
2	Σ_g	2212	2111	0.00
3	Σ_g	868	828	0.00
4	Σ_u	3472	3314	123.28
5	Σ_u	2005	1914	0.30
6	Π_g	577	551	0.00
6	Π_g	577	551	0.00
7	Π_g	740i	706i	0.00
7	Π_g	740i	706i	0.00
8	Π_u	521	497	104.64
8	Π_u	521	497	104.64
9	Π_u	120	114	0.39
9	Π_u	120	114	0.39

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	1.918
C4	0.000	0.000	-1.918
H5	0.000	0.000	2.983
H6	0.000	0.000	-2.983

	C1	C2	C3	C4	H5	H6
C1		1.3821	1.2266	2.6087	2.2921	3.6741
C2	1.3821		2.6087	1.2266	3.6741	2.2921
C3	1.2266	2.6087		3.8353	1.0654	4.9008
C4	2.6087	1.2266	3.8353		4.9008	1.0654
H5	2.2921	3.6741	1.0654	4.9008		5.9662
H6	3.6741	2.2921	4.9008	1.0654	5.9662

All results from a given calculation for C₄H₂ (Diacetylene)

using model chemistry: MP2/3-21G

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	-152.012566
Energy at 298.15K	-152.011466
HF Energy	-151.646711
Nuclear repulsion energy	76.312506

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3481	3322	0.00
2	A_g	2213	2112	0.00
3	A_g	878	838	0.00
4	A_g	735	701	0.00
5	A_g	587	561	0.00
6	A_u	598	570	98.56
7	A_u	184	175	3.07
8	B_g	614	586	0.00
9	B_u	3480	3322	121.22
10	B_u	2009	1918	0.26
11	B_u	658	628	95.19
12	B_u	209	199	6.16

Atom	x (Å)	y (Å)
C1	-0.034	0.690
C2	0.034	-0.690
C3	0.034	1.914
C4	-0.034	-1.914
H5	0.009	2.979
H6	-0.009	-2.979

	C1	C2	C3	C4	H5	H6
C1		1.3808	1.2268	2.6040	2.2898	3.6686
C2	1.3808		2.6040	1.2268	3.6686	2.2898
C3	1.2268	2.6040		3.8296	1.0648	4.8937
C4	2.6040	1.2268	3.8296		4.8937	1.0648
H5	2.2898	3.6686	1.0648	4.8937		5.9580
H6	3.6686	2.2898	4.8937	1.0648	5.9580

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	173.944		C1	C3	H5	175.443
C2	C1	C3	173.944		C2	C4	H6	175.443

All results from a given calculation for C4H2 (Diacetylene)

using model chemistry: MP2/3-21G

States and conformations

Conformer 1 (D*H)

Conformer 2 (C2H)

All results from a given calculation for C₄H₂ (Diacetylene)