CCCBDB calculation results Page

State	Conformation	minimum conformation	conformer description	state description
1	1	yes	D2H	¹A_g
1	2	no	D4H	¹A_1g

Conformer 1 (D2H)

Jump to S1C2

Energy calculated at wB97X-D/cc-pVDZ

	hartrees
Energy at 0K	-154.633086
Energy at 298.15K	-154.636224
HF Energy	-154.633086
Nuclear repulsion energy	98.915875

The energy at 298.15K was derived from the energy at 0K and an integrated heat capacity that used the calculated vibrational frequencies.

Vibrational Frequencies calculated at wB97X-D/cc-pVDZ

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3302	3146	0.00
2	A_g	1666	1587	0.00
3	A_g	1145	1091	0.00
4	A_g	983	937	0.00
5	A_u	900	857	0.00
6	A_u	538	512	0.00
7	B_1g	905	862	0.00
8	B_1u	3291	3135	19.16
9	B_1u	1678	1598	7.68
10	B_1u	1085	1033	0.99
11	B_2g	617	587	0.00
12	B_2u	3269	3115	10.70
13	B_2u	1295	1233	41.45
14	B_2u	749	713	9.14
15	B_3g	3255	3101	0.00
16	B_3g	1216	1159	0.00
17	B_3g	854	814	0.00
18	B_3u	609	580	174.25

Unscaled Zero Point Vibrational Energy (zpe) 13678.0 cm^-1
Scaled (by 0.9526) Zero Point Vibrational Energy (zpe) 13029.7 cm^-1
See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.

Rotational Constants (cm^-1) from geometry optimized at wB97X-D/cc-pVDZ

A	B	C
0.56844	0.42971	0.24472

See section I.F.4 to change rotational constant units

Geometric Data calculated at wB97X-D/cc-pVDZ

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.668	0.785
C2	0.668	-0.785
C3	-0.668	0.785
C4	-0.668	-0.785
H5	1.437	1.547
H6	1.437	-1.547
H7	-1.437	1.547
H8	-1.437	-1.547

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.5703	1.3354	2.0614	1.0831	2.4562	2.2387	3.1419
C2	1.5703		2.0614	1.3354	2.4562	1.0831	3.1419	2.2387
C3	1.3354	2.0614		1.5703	2.2387	3.1419	1.0831	2.4562
C4	2.0614	1.3354	1.5703		3.1419	2.2387	2.4562	1.0831
H5	1.0831	2.4562	2.2387	3.1419		3.0947	2.8745	4.2237
H6	2.4562	1.0831	3.1419	2.2387	3.0947		4.2237	2.8745
H7	2.2387	3.1419	1.0831	2.4562	2.8745	4.2237		3.0947
H8	3.1419	2.2387	2.4562	1.0831	4.2237	2.8745	3.0947

picture of cyclobutadiene state 1 conformation 1

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
C1	C2	C4	90.000	C1	C2	H6	134.724
C1	C3	C4	90.000	C1	C3	H7	135.276
C2	C1	C3	90.000	C2	C1	H5	134.724
C2	C4	C3	90.000	C3	C1	H5	135.276
C4	C2	H6	135.276	C4	C3	H7	134.724

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at wB97X-D/cc-pVDZ Charges (e)

Number	Element	Mulliken
1	C	-0.161
2	C	-0.161
3	C	-0.161
4	C	-0.161
5	H	0.161
6	H	0.161
7	H	0.161
8	H	0.161

Electric dipole moments
Electric dipole components in Debye
(What's a Debye? See section VII.A.3)

	x	y	z	Total
	0.000	0.000	0.000	0.000
CHELPG
AIM
ESP

Electric Quadrupole moment
Quadrupole components in D Å

Primitive
	x	y	z
x	-27.138	0.000	0.000
y	0.000	-20.675	0.000
z	0.000	0.000	-22.241

Traceless
	x	y	z
x	-5.680	0.000	0.000
y	0.000	4.014	0.000
z	0.000	0.000	1.666

Polar
3z²-r²	3.332
x²-y²	-6.463
xy	0.000
xz	0.000
yz	0.000

Polarizabilities
Components of the polarizability tensor.
Units are Å³ (Angstrom cubed)
Change units.

	x	y	z
x	4.337	0.000	0.000
y	0.000	7.677	0.000
z	0.000	0.000	6.105

<r²> (average value of r²) Å²

<r²>	57.866
(<r²>)^1/2	7.607

Conformer 2 (D4H)

Jump to S1C1

Energy calculated at wB97X-D/cc-pVDZ

	hartrees
Energy at 0K	-154.575727
Energy at 298.15K
HF Energy	-154.575727
Nuclear repulsion energy	99.639396

The energy at 298.15K was derived from the energy at 0K and an integrated heat capacity that used the calculated vibrational frequencies.

Vibrational Frequencies calculated at wB97X-D/cc-pVDZ

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3374	3214	0.00
2	A_g	3182	3031	0.00
3	A_g	1323	1261	0.00
4	A_g	958	912	0.00
5	B_1g	1112	1059	0.00
6	B_1u	3366	3206	18.99
7	B_1u	1488	1417	124.90
8	B_1u	989	942	186.33
9	B_2g	436i	415i	0.00
10	B_2u	3188	3037	59.71
11	B_2u	1330	1267	164.68
12	B_2u	971	925	1.58
13	B_3g	2563	2442	0.00
14	B_3g	1214	1156	0.00
15	B_3g	1039	989	0.00
16	B_3u	939	894	0.21
17	B_3u	525	500	149.46
18	B_3u	449i	428i	181.54

Unscaled Zero Point Vibrational Energy (zpe) 13336.4 cm^-1
Scaled (by 0.9526) Zero Point Vibrational Energy (zpe) 12704.3 cm^-1
See section III.C.1 List or set vibrational scaling factors to change the scale factors used here.
See section III.C.2 Calculate a vibrational scaling factor for a given set of molecules to determine the least squares best scaling factor.

Rotational Constants (cm^-1) from geometry optimized at wB97X-D/cc-pVDZ

A	B	C
0.55001	0.46190	0.25106

See section I.F.4 to change rotational constant units

Geometric Data calculated at wB97X-D/cc-pVDZ

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.000	1.069
C2	0.957	0.000
C3	-0.957	0.000
C4	0.000	-1.069
H5	0.000	2.147
H6	2.042	0.000
H7	-2.042	0.000
H8	0.000	-2.147

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.4342	1.4342	2.1371	1.0780	2.3047	2.3047	3.2150
C2	1.4342		1.9133	1.4342	2.3500	1.0854	2.9987	2.3500
C3	1.4342	1.9133		1.4342	2.3500	2.9987	1.0854	2.3500
C4	2.1371	1.4342	1.4342		3.2150	2.3047	2.3047	1.0780
H5	1.0780	2.3500	2.3500	3.2150		2.9627	2.9627	4.2930
H6	2.3047	1.0854	2.9987	2.3047	2.9627		4.0841	2.9627
H7	2.3047	2.9987	1.0854	2.3047	2.9627	4.0841		2.9627
H8	3.2150	2.3500	2.3500	1.0780	4.2930	2.9627	2.9627

picture of cyclobutadiene state 1 conformation 2

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
C1	C2	C4	96.325	C1	C2	H6	131.838
C1	C3	C4	96.325	C1	C3	H7	131.838
C2	C1	C3	83.675	C2	C1	H5	138.162
C2	C4	C3	83.675	C3	C1	H5	138.162
C4	C2	H6	131.838	C4	C3	H7	131.838

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at wB97X-D/cc-pVDZ Charges (e)

Number	Element	Mulliken
1	C	-0.553
2	C	0.219
3	C	0.219
4	C	-0.553
5	H	0.165
6	H	0.169
7	H	0.169
8	H	0.165

Electric dipole moments
Electric dipole components in Debye
(What's a Debye? See section VII.A.3)

	x	y	z	Total
	0.000	0.000	0.000	0.000
CHELPG
AIM
ESP

Electric Quadrupole moment
Quadrupole components in D Å

Primitive
	x	y	z
x	-28.086	0.000	0.000
y	0.000	-18.347	0.000
z	0.000	0.000	-25.809

Traceless
	x	y	z
x	-6.008	0.000	0.000
y	0.000	8.601	0.000
z	0.000	0.000	-2.593

Polar
3z²-r²	-5.185
x²-y²	-9.739
xy	0.000
xz	0.000
yz	0.000

Polarizabilities
Components of the polarizability tensor.
Units are Å³ (Angstrom cubed)
Change units.

	x	y	z
x	5.232	0.000	0.000
y	0.000	6.881	0.000
z	0.000	0.000	9.457

<r²> (average value of r²) Å²

<r²>	57.335
(<r²>)^1/2	7.572

All results from a given calculation for C₄H₄ (cyclobutadiene)

using model chemistry: wB97X-D/cc-pVDZ

States and conformations

Conformer 1 (D2H)

Conformer 2 (D4H)

	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: wB97X-D/cc-pVDZ

States and conformations

Conformer 1 (D2H)

Conformer 2 (D4H)

All results from a given calculation for C₄H₄ (cyclobutadiene)