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 B97D3/cc-pVTZ

	hartrees
Energy at 0K	-154.626172
Energy at 298.15K	-154.629132
HF Energy	-154.626172
Nuclear repulsion energy	98.436290

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 B97D3/cc-pVTZ

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3185	3140	0.00
2	A_g	1587	1565	0.00
3	A_g	1085	1070	0.00
4	A_g	929	916	0.00
5	A_u	846	834	0.00
6	A_u	522	515	0.00
7	B_1g	844	832	0.00
8	B_1u	3174	3129	33.86
9	B_1u	1585	1563	4.81
10	B_1u	1034	1020	0.04
11	B_2g	570	562	0.00
12	B_2u	3152	3108	22.49
13	B_2u	1225	1208	38.75
14	B_2u	653	643	7.52
15	B_3g	3137	3093	0.00
16	B_3g	1155	1139	0.00
17	B_3g	853	841	0.00
18	B_3u	557	550	118.31

Unscaled Zero Point Vibrational Energy (zpe) 13047.0 cm^-1
Scaled (by 0.986) Zero Point Vibrational Energy (zpe) 12864.4 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 B97D3/cc-pVTZ

A	B	C
0.56612	0.42261	0.24198

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

Geometric Data calculated at B97D3/cc-pVTZ

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.668	0.792
C2	0.668	-0.792
C3	-0.668	0.792
C4	-0.668	-0.792
H5	1.438	1.555
H6	1.438	-1.555
H7	-1.438	1.555
H8	-1.438	-1.555

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.5847	1.3367	2.0732	1.0837	2.4707	2.2403	3.1541
C2	1.5847		2.0732	1.3367	2.4707	1.0837	3.1541	2.2403
C3	1.3367	2.0732		1.5847	2.2403	3.1541	1.0837	2.4707
C4	2.0732	1.3367	1.5847		3.1541	2.2403	2.4707	1.0837
H5	1.0837	2.4707	2.2403	3.1541		3.1107	2.8760	4.2365
H6	2.4707	1.0837	3.1541	2.2403	3.1107		4.2365	2.8760
H7	2.2403	3.1541	1.0837	2.4707	2.8760	4.2365		3.1107
H8	3.1541	2.2403	2.4707	1.0837	4.2365	2.8760	3.1107

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	134.709
C1	C3	C4	90.000	C1	C3	H7	135.291
C2	C1	C3	90.000	C2	C1	H5	134.709
C2	C4	C3	90.000	C3	C1	H5	135.291
C4	C2	H6	135.291	C4	C3	H7	134.709

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at B97D3/cc-pVTZ Charges (e)

Number	Element	Mulliken
1	C	-0.097
2	C	-0.097
3	C	-0.097
4	C	-0.097
5	H	0.097
6	H	0.097
7	H	0.097
8	H	0.097

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	-26.528	0.000	0.000
y	0.000	-20.987	0.000
z	0.000	0.000	-22.219

Traceless
	x	y	z
x	-4.924	0.000	0.000
y	0.000	3.386	0.000
z	0.000	0.000	1.539

Polar
3z²-r²	3.077
x²-y²	-5.540
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	3.773	0.000	0.000
y	0.000	7.642	0.000
z	0.000	0.000	6.547

<r²> (average value of r²) Å²

<r²>	58.255
(<r²>)^1/2	7.633

Conformer 2 (D4H)

Jump to S1C1

Energy calculated at B97D3/cc-pVTZ

	hartrees
Energy at 0K	-154.626172
Energy at 298.15K	-154.629131
HF Energy	-154.626172
Nuclear repulsion energy	98.437475

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 B97D3/cc-pVTZ

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)
1	A_g	3185	3140	0.00
2	A_g	1588	1565	0.00
3	A_g	1085	1070	0.00
4	A_g	929	916	0.00
5	A_u	846	834	0.00
6	A_u	522	515	0.00
7	B_1g	844	832	0.00
8	B_1u	3174	3129	33.80
9	B_1u	1586	1564	4.83
10	B_1u	1034	1020	0.03
11	B_2g	569	561	0.00
12	B_2u	3152	3108	22.47
13	B_2u	1226	1208	38.81
14	B_2u	652	643	7.58
15	B_3g	3137	3093	0.00
16	B_3g	1156	1139	0.00
17	B_3g	853	841	0.00
18	B_3u	557	549	118.39

Unscaled Zero Point Vibrational Energy (zpe) 13047.2 cm^-1
Scaled (by 0.986) Zero Point Vibrational Energy (zpe) 12864.6 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 B97D3/cc-pVTZ

A	B	C
0.56642	0.42243	0.24197

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

Geometric Data calculated at B97D3/cc-pVTZ

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
C1	0.668	0.792
C2	0.668	-0.792
C3	-0.668	0.792
C4	-0.668	-0.792
H5	1.437	1.556
H6	1.437	-1.556
H7	-1.437	1.556
H8	-1.437	-1.556

Atom - Atom Distances (Å)

	C1	C2	C3	C4	H5	H6	H7	H8
C1		1.5849	1.3366	2.0732	1.0837	2.4714	2.2395	3.1542
C2	1.5849		2.0732	1.3366	2.4714	1.0837	3.1542	2.2395
C3	1.3366	2.0732		1.5849	2.2395	3.1542	1.0837	2.4714
C4	2.0732	1.3366	1.5849		3.1542	2.2395	2.4714	1.0837
H5	1.0837	2.4714	2.2395	3.1542		3.1128	2.8738	4.2366
H6	2.4714	1.0837	3.1542	2.2395	3.1128		4.2366	2.8738
H7	2.2395	3.1542	1.0837	2.4714	2.8738	4.2366		3.1128
H8	3.1542	2.2395	2.4714	1.0837	4.2366	2.8738	3.1128

picture of cyclobutadiene state 1 conformation 2

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
C1	C2	C4	90.000	C1	C2	H6	135.326
C1	C3	C4	90.000	C1	C3	H7	134.674
C2	C1	C3	90.000	C2	C1	H5	135.326
C2	C4	C3	90.000	C3	C1	H5	134.674
C4	C2	H6	134.674	C4	C3	H7	135.326

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at B97D3/cc-pVTZ Charges (e)

Number	Element	Mulliken
1	C	-0.097
2	C	-0.097
3	C	-0.097
4	C	-0.097
5	H	0.097
6	H	0.097
7	H	0.097
8	H	0.097

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	-26.527	0.000	0.000
y	0.000	-20.999	0.000
z	0.000	0.000	-22.207

Traceless
	x	y	z
x	-4.924	0.000	0.000
y	0.000	3.369	0.000
z	0.000	0.000	1.556

Polar
3z²-r²	3.112
x²-y²	-5.529
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	3.773	0.000	0.000
y	0.000	7.639	0.000
z	0.000	0.000	6.549

<r²> (average value of r²) Å²

<r²>	58.256
(<r²>)^1/2	7.633

All results from a given calculation for C₄H₄ (cyclobutadiene)

using model chemistry: B97D3/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: B97D3/cc-pVTZ

States and conformations

Conformer 1 (D2H)

Conformer 2 (D4H)

All results from a given calculation for C₄H₄ (cyclobutadiene)