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	hartrees
Energy at 0K	-153.127123
Energy at 298.15K	-153.130016
HF Energy	-152.767454
Nuclear repulsion energy	96.884158

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3299	3149	0.00
2	A_g	1522	1452	0.00
3	A_g	1123	1072	0.00
4	A_g	907	866	0.00
5	A_u	740	707	0.00
6	A_u	500	477	0.00
7	B_1g	828	790	0.00
8	B_1u	3282	3133	16.53
9	B_1u	1510	1441	2.60
10	B_1u	1077	1028	0.34
11	B_2g	551	526	0.00
12	B_2u	3261	3112	8.17
13	B_2u	1285	1226	31.31
14	B_2u	603	576	3.84
15	B_3g	3248	3100	0.00
16	B_3g	1221	1165	0.00
17	B_3g	888	848	0.00
18	B_3u	593	566	169.78

Atom	y (Å)	z (Å)
C1	0.680	0.812
C2	0.680	-0.812
C3	-0.680	0.812
C4	-0.680	-0.812
H5	1.448	1.570
H6	1.448	-1.570
H7	-1.448	1.570
H8	-1.448	-1.570

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.6231	1.3591	2.1170	1.0803	2.5030	2.2592	3.1940
C2	1.6231		2.1170	1.3591	2.5030	1.0803	3.1940	2.2592
C3	1.3591	2.1170		1.6231	2.2592	3.1940	1.0803	2.5030
C4	2.1170	1.3591	1.6231		3.1940	2.2592	2.5030	1.0803
H5	1.0803	2.5030	2.2592	3.1940		3.1409	2.8967	4.2727
H6	2.5030	1.0803	3.1940	2.2592	3.1409		4.2727	2.8967
H7	2.2592	3.1940	1.0803	2.5030	2.8967	4.2727		3.1409
H8	3.1940	2.2592	2.5030	1.0803	4.2727	2.8967	3.1409

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
C1	C2	C4	90.000	C1	C2	H6	134.630
C1	C3	C4	90.000	C1	C3	H7	135.370
C2	C1	C3	90.000	C2	C1	H5	134.630
C2	C4	C3	90.000	C3	C1	H5	135.370
C4	C2	H6	135.370	C4	C3	H7	134.630

All results from a given calculation for C₄H₄ (cyclobutadiene)

using model chemistry: MP2/3-21G

States and conformations

	Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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All results from a given calculation for C4H4 (cyclobutadiene)

using model chemistry: MP2/3-21G

States and conformations

All results from a given calculation for C₄H₄ (cyclobutadiene)