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/6-31G*

	hartrees
Energy at 0K	-154.619747
Energy at 298.15K	-154.622856
HF Energy	-154.619747
Nuclear repulsion energy

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/6-31G*

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3306	3136	0.00
2	A_g	1682	1596	0.00
3	A_g	1150	1091	0.00
4	A_g	986	936	0.00
5	A_u	900	854	0.00
6	A_u	547	519	0.00
7	B_1g	882	837	0.00
8	B_1u	3295	3125	25.88
9	B_1u	1695	1608	2.64
10	B_1u	1090	1034	0.31
11	B_2g	613	581	0.00
12	B_2u	3273	3105	14.35
13	B_2u	1300	1233	37.11
14	B_2u	750	712	8.06
15	B_3g	3258	3090	0.00
16	B_3g	1214	1151	0.00
17	B_3g	853	809	0.00
18	B_3u	608	577	131.83

Unscaled Zero Point Vibrational Energy (zpe) 13701.0 cm^-1
Scaled (by 0.9485) Zero Point Vibrational Energy (zpe) 12995.4 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/6-31G*

A	B	C
0.57002	0.42931	0.24488

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

Geometric Data calculated at wB97X-D/6-31G*

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.666	0.786
C2	0.666	-0.786
C3	-0.666	0.786
C4	-0.666	-0.786
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		1.5714	1.3327	2.0604	1.0837	2.4570	2.2373	3.1414
C2	1.5714		2.0604	1.3327	2.4570	1.0837	3.1414	2.2373
C3	1.3327	2.0604		1.5714	2.2373	3.1414	1.0837	2.4570
C4	2.0604	1.3327	1.5714		3.1414	2.2373	2.4570	1.0837
H5	1.0837	2.4570	2.2373	3.1414		3.0945	2.8747	4.2237
H6	2.4570	1.0837	3.1414	2.2373	3.0945		4.2237	2.8747
H7	2.2373	3.1414	1.0837	2.4570	2.8747	4.2237		3.0945
H8	3.1414	2.2373	2.4570	1.0837	4.2237	2.8747	3.0945

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	134.645
C1	C3	C4	90.000	C1	C3	H7	135.355
C2	C1	C3	90.000	C2	C1	H5	134.645
C2	C4	C3	90.000	C3	C1	H5	135.355
C4	C2	H6	135.355	C4	C3	H7	134.645

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at wB97X-D/6-31G* Charges (e)

Number	Element	Mulliken
1	C	-0.172
2	C	-0.172
3	C	-0.172
4	C	-0.172
5	H	0.172
6	H	0.172
7	H	0.172
8	H	0.172

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	-26.005	0.000	0.000
y	0.000	-20.269	0.000
z	0.000	0.000	-21.357

Traceless
	x	y	z
x	-5.193	0.000	0.000
y	0.000	3.412	0.000
z	0.000	0.000	1.781

Polar
3z²-r²	3.561
x²-y²	-5.736
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	2.304	0.000	0.000
y	0.000	6.924	0.000
z	0.000	0.000	5.478

<r²> (average value of r²) Å²

<r²>	57.339
(<r²>)^1/2	7.572

Conformer 2 (D4H)

Jump to S1C1

Energy calculated at wB97X-D/6-31G*

	hartrees
Energy at 0K	-154.559059
Energy at 298.15K
HF Energy	-154.559059
Nuclear repulsion energy

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/6-31G*

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3383	3208	0.00
2	A_g	3181	3017	0.00
3	A_g	1331	1262	0.00
4	A_g	961	911	0.00
5	B_1g	1128	1070	0.00
6	B_1u	3374	3201	11.09
7	B_1u	1516	1438	68.84
8	B_1u	1000	949	132.48
9	B_2g	531i	504i	0.00
10	B_2u	3185	3021	81.00
11	B_2u	1333	1264	146.38
12	B_2u	974	924	1.57
13	B_3g	2582	2449	0.00
14	B_3g	1217	1155	0.00
15	B_3g	1042	988	0.00
16	B_3u	952	903	4.02
17	B_3u	523	496	79.65
18	B_3u	470i	445i	190.62

Unscaled Zero Point Vibrational Energy (zpe) 13340.3 cm^-1
Scaled (by 0.9485) Zero Point Vibrational Energy (zpe) 12653.3 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/6-31G*

A	B	C
0.55351	0.46094	0.25150

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

Geometric Data calculated at wB97X-D/6-31G*

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.000	1.068
C2	0.954	0.000
C3	-0.954	0.000
C4	0.000	-1.068
H5	0.000	2.146
H6	2.040	0.000
H7	-2.040	0.000
H8	0.000	-2.146

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.4320	1.4320	2.1353	1.0781	2.3027	2.3027	3.2134
C2	1.4320		1.9088	1.4320	2.3484	1.0859	2.9947	2.3484
C3	1.4320	1.9088		1.4320	2.3484	2.9947	1.0859	2.3484
C4	2.1353	1.4320	1.4320		3.2134	2.3027	2.3027	1.0781
H5	1.0781	2.3484	2.3484	3.2134		2.9609	2.9609	4.2914
H6	2.3027	1.0859	2.9947	2.3027	2.9609		4.0806	2.9609
H7	2.3027	2.9947	1.0859	2.3027	2.9609	4.0806		2.9609
H8	3.2134	2.3484	2.3484	1.0781	4.2914	2.9609	2.9609

picture of cyclobutadiene state 1 conformation 2

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
C1	C2	C4	96.411	C1	C2	H6	131.794
C1	C3	C4	96.411	C1	C3	H7	131.794
C2	C1	C3	83.589	C2	C1	H5	138.206
C2	C4	C3	83.589	C3	C1	H5	138.206
C4	C2	H6	131.794	C4	C3	H7	131.794

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at wB97X-D/6-31G* Charges (e)

Number	Element	Mulliken
1	C	-0.330
2	C	-0.018
3	C	-0.018
4	C	-0.330
5	H	0.158
6	H	0.190
7	H	0.190
8	H	0.158

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	-26.347	0.000	0.000
y	0.000	-18.075	0.000
z	0.000	0.000	-24.235

Traceless
	x	y	z
x	-5.192	0.000	0.000
y	0.000	7.216	0.000
z	0.000	0.000	-2.024

Polar
3z²-r²	-4.048
x²-y²	-8.272
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	2.336	0.000	0.000
y	0.000	6.548	0.000
z	0.000	0.000	7.178

<r²> (average value of r²) Å²

<r²>	56.524
(<r²>)^1/2	7.518

All results from a given calculation for C₄H₄ (cyclobutadiene)

using model chemistry: wB97X-D/6-31G*

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/6-31G*

States and conformations

Conformer 1 (D2H)

Conformer 2 (D4H)

All results from a given calculation for C₄H₄ (cyclobutadiene)