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-pVTZ

	hartrees
Energy at 0K	-154.675062
Energy at 298.15K	-154.678230
HF Energy	-154.675062
Nuclear repulsion energy	99.271368

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-pVTZ

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3282	3137	0.00
2	A_g	1663	1590	0.00
3	A_g	1143	1093	0.00
4	A_g	979	936	0.00
5	A_u	921	881	0.00
6	A_u	546	522	0.00
7	B_1g	923	883	0.00
8	B_1u	3270	3126	17.26
9	B_1u	1671	1598	4.08
10	B_1u	1087	1039	0.25
11	B_2g	632	604	0.00
12	B_2u	3248	3105	10.23
13	B_2u	1296	1239	41.20
14	B_2u	740	707	10.05
15	B_3g	3234	3091	0.00
16	B_3g	1222	1168	0.00
17	B_3g	858	820	0.00
18	B_3u	615	588	134.11

Unscaled Zero Point Vibrational Energy (zpe) 13663.9 cm^-1
Scaled (by 0.956) Zero Point Vibrational Energy (zpe) 13062.7 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-pVTZ

A	B	C
0.57528	0.43067	0.24629

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

Geometric Data calculated at wB97X-D/cc-pVTZ

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.663	0.784
C2	0.663	-0.784
C3	-0.663	0.784
C4	-0.663	-0.784
H5	1.429	1.544
H6	1.429	-1.544
H7	-1.429	1.544
H8	-1.429	-1.544

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.5686	1.3262	2.0541	1.0788	2.4512	2.2257	3.1302
C2	1.5686		2.0541	1.3262	2.4512	1.0788	3.1302	2.2257
C3	1.3262	2.0541		1.5686	2.2257	3.1302	1.0788	2.4512
C4	2.0541	1.3262	1.5686		3.1302	2.2257	2.4512	1.0788
H5	1.0788	2.4512	2.2257	3.1302		3.0885	2.8576	4.2077
H6	2.4512	1.0788	3.1302	2.2257	3.0885		4.2077	2.8576
H7	2.2257	3.1302	1.0788	2.4512	2.8576	4.2077		3.0885
H8	3.1302	2.2257	2.4512	1.0788	4.2077	2.8576	3.0885

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	134.784
C1	C3	C4	90.000	C1	C3	H7	135.216
C2	C1	C3	90.000	C2	C1	H5	134.784
C2	C4	C3	90.000	C3	C1	H5	135.216
C4	C2	H6	135.216	C4	C3	H7	134.784

Electronic energy levels

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

Number	Element	Mulliken
1	C	-0.116
2	C	-0.116
3	C	-0.116
4	C	-0.116
5	H	0.116
6	H	0.116
7	H	0.116
8	H	0.116

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	-26.556	0.000	0.000
y	0.000	-20.620	0.000
z	0.000	0.000	-21.976

Traceless
	x	y	z
x	-5.258	0.000	0.000
y	0.000	3.646	0.000
z	0.000	0.000	1.612

Polar
3z²-r²	3.225
x²-y²	-5.936
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	3.736	0.000	0.000
y	0.000	7.448	0.000
z	0.000	0.000	6.224

<r²> (average value of r²) Å²

<r²>	57.400
(<r²>)^1/2	7.576

Conformer 2 (D4H)

Jump to S1C1

Energy calculated at wB97X-D/cc-pVTZ

	hartrees
Energy at 0K	-154.616319
Energy at 298.15K
HF Energy	-154.616319
Nuclear repulsion energy	99.997826

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-pVTZ

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3357	3210	0.00
2	A_g	3157	3018	0.00
3	A_g	1315	1257	0.00
4	A_g	959	916	0.00
5	B_1g	1118	1069	0.00
6	B_1u	3348	3201	15.56
7	B_1u	1478	1413	87.75
8	B_1u	980	937	162.30
9	B_2g	474i	453i	0.00
10	B_2u	3162	3023	58.47
11	B_2u	1318	1260	149.25
12	B_2u	959	917	2.42
13	B_3g	2638	2522	0.00
14	B_3g	1207	1154	0.00
15	B_3g	1028	983	0.00
16	B_3u	953	911	1.14
17	B_3u	521	498	99.21
18	B_3u	470i	449i	146.74

Unscaled Zero Point Vibrational Energy (zpe) 13276.9 cm^-1
Scaled (by 0.956) Zero Point Vibrational Energy (zpe) 12692.7 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-pVTZ

A	B	C
0.55423	0.46502	0.25286

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

Geometric Data calculated at wB97X-D/cc-pVTZ

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.951	0.000
C2	0.000	1.066
C3	0.000	-1.066
C4	-0.951	0.000
H5	2.034	0.000
H6	0.000	2.140
H7	0.000	-2.140
H8	-2.034	0.000

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.4290	1.4290	1.9028	1.0822	2.3419	2.3419	2.9850
C2	1.4290		2.1326	1.4290	2.2962	1.0736	3.2062	2.2962
C3	1.4290	2.1326		1.4290	2.2962	3.2062	1.0736	2.2962
C4	1.9028	1.4290	1.4290		2.9850	2.3419	2.3419	1.0822
H5	1.0822	2.2962	2.2962	2.9850		2.9521	2.9521	4.0672
H6	2.3419	1.0736	3.2062	2.3419	2.9521		4.2798	2.9521
H7	2.3419	3.2062	1.0736	2.3419	2.9521	4.2798		2.9521
H8	2.9850	2.2962	2.2962	1.0822	4.0672	2.9521	2.9521

picture of cyclobutadiene state 1 conformation 2

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
C1	C2	C4	83.480	C1	C2	H6	138.260
C1	C3	C4	83.480	C1	C3	H7	138.260
C2	C1	C3	96.520	C2	C1	H5	131.740
C2	C4	C3	96.520	C3	C1	H5	131.740
C4	C2	H6	138.260	C4	C3	H7	138.260

Electronic energy levels

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

Number	Element	Mulliken
1	C	0.177
2	C	-0.425
3	C	-0.425
4	C	0.177
5	H	0.116
6	H	0.133
7	H	0.133
8	H	0.116

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	-27.104	0.000	0.000
y	0.000	-18.281	0.000
z	0.000	0.000	-25.027

Traceless
	x	y	z
x	-5.450	0.000	0.000
y	0.000	7.784	0.000
z	0.000	0.000	-2.335

Polar
3z²-r²	-4.670
x²-y²	-8.823
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	3.964	0.000	0.000
y	0.000	6.927	0.000
z	0.000	0.000	8.198

<r²> (average value of r²) Å²

<r²>	56.652
(<r²>)^1/2	7.527

All results from a given calculation for C₄H₄ (cyclobutadiene)

using model chemistry: wB97X-D/cc-pVTZ

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-pVTZ

States and conformations

Conformer 1 (D2H)

Conformer 2 (D4H)

All results from a given calculation for C₄H₄ (cyclobutadiene)