	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 Si₂H₄ (Disilene)

using model chemistry: PBEPBE/3-21G

19 10 17 12 22

States and conformations

State	Conformation	minimum conformation	conformer description	state description
1	1	no	D2H	¹A_G
1	2	yes	C2H	¹A_G
1	3	no	C2V	¹A₁

Conformer 1 (D2H)

Jump to S1C2 S1C3

Energy calculated at PBEPBE/3-21G

	hartrees
Energy at 0K	-577.925230
Energy at 298.15K
HF Energy	-577.925230
Nuclear repulsion energy	77.831476

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 PBEPBE/3-21G

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)	Raman Act (Å⁴/u)	Dep P	Dep U
1	A_g	2175	2156	0.00	346.94	0.17	0.29
2	A_g	883	875	0.00	30.02	0.70	0.82
3	A_g	567	562	0.00	58.97	0.28	0.44
4	A_u	540	535	0.00	0.00	0.00	0.00
5	B_1u	2169	2149	59.30	0.00	0.00	0.00
6	B_1u	808	801	95.23	0.00	0.00	0.00
7	B_2g	193i	192i	0.00	51.14	0.75	0.86
8	B_2u	2215	2195	130.12	0.00	0.00	0.00
9	B_2u	354	351	10.56	0.00	0.00	0.00
10	B_3g	2202	2182	0.00	172.50	0.75	0.86
11	B_3g	563	558	0.00	7.24	0.75	0.86
12	B_3u	478	474	0.00	0.00	0.00	0.00

Unscaled Zero Point Vibrational Energy (zpe) 6380.4 cm^-1
Scaled (by 0.9909) Zero Point Vibrational Energy (zpe) 6322.3 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 PBEPBE/3-21G

A	B	C
2.57224	0.21176	0.19565

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

Geometric Data calculated at PBEPBE/3-21G

Point Group is D_2h

Cartesians (Å)

Atom	y (Å)	z (Å)
Si1	0.000	1.082
Si2	0.000	-1.082
H3	1.275	1.873
H4	-1.275	1.873
H5	1.275	-1.873
H6	-1.275	-1.873

Atom - Atom Distances (Å)

	Si1	Si2	H3	H4	H5	H6
Si1		2.1633	1.5006	1.5006	3.2180	3.2180
Si2	2.1633		3.2180	3.2180	1.5006	1.5006
H3	1.5006	3.2180		2.5501	3.7460	4.5316
H4	1.5006	3.2180	2.5501		4.5316	3.7460
H5	3.2180	1.5006	3.7460	4.5316		2.5501
H6	3.2180	1.5006	4.5316	3.7460	2.5501

picture of Disilene state 1 conformation 1

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
Si1	Si2	H5	121.826	Si1	Si2	H6	121.826
Si2	Si1	H3	121.826	Si2	Si1	H4	121.826
H3	Si1	H4	116.348	H5	Si2	H6	116.348

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at PBEPBE/3-21G Charges (e)

Number	Element	Mulliken
1	Si	0.083
2	Si	0.083
3	H	-0.042
4	H	-0.042
5	H	-0.042
6	H	-0.042

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	-32.209	0.000	0.000
y	0.000	-29.621	0.000
z	0.000	0.000	-28.097

Traceless
	x	y	z
x	-3.350	0.000	0.000
y	0.000	0.532	0.000
z	0.000	0.000	2.818

Polar
3z²-r²	5.636
x²-y²	-2.588
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	4.338	0.000	0.000
y	0.000	6.101	0.000
z	0.000	0.000	13.600

<r²> (average value of r²) Å²

<r²>	72.017
(<r²>)^1/2	8.486

Conformer 2 (C2H)

Jump to S1C1 S1C3

Energy calculated at PBEPBE/3-21G

	hartrees
Energy at 0K	-577.925895
Energy at 298.15K
HF Energy	-577.925895
Nuclear repulsion energy	77.322860

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 PBEPBE/3-21G

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)	Raman Act (Å⁴/u)	Dep P	Dep U
1	A_g	2150	2130	0.00	349.59	0.15	0.26
2	A_g	886	878	0.00	41.86	0.66	0.80
3	A_g	548	543	0.00	51.10	0.37	0.54
4	A_g	265	263	0.00	37.18	0.35	0.51
5	A_u	2189	2169	152.98	0.00	0.00	0.00
6	A_u	523	518	0.03	0.00	0.00	0.00
7	A_u	342	339	10.66	0.00	0.00	0.00
8	B_g	2175	2155	0.00	204.47	0.75	0.86
9	B_g	578	573	0.00	12.04	0.75	0.86
10	B_u	2145	2126	91.21	0.00	0.00	0.00
11	B_u	848	840	139.85	0.00	0.00	0.00
12	B_u	427	423	17.82	0.00	0.00	0.00

Unscaled Zero Point Vibrational Energy (zpe) 6537.9 cm^-1
Scaled (by 0.9909) Zero Point Vibrational Energy (zpe) 6478.4 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 PBEPBE/3-21G

A	B	C
2.45645	0.20842	0.19427

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

Geometric Data calculated at PBEPBE/3-21G

Point Group is C_2h

Cartesians (Å)

Atom	x (Å)	y (Å)	z (Å)
Si1	0.000	1.093	0.000
Si2	0.000	-1.093	0.000
H3	0.381	1.828	1.258
H4	0.381	1.828	-1.258
H5	-0.381	-1.828	1.258
H6	-0.381	-1.828	-1.258

Atom - Atom Distances (Å)

	Si1	Si2	H3	H4	H5	H6
Si1		2.1856	1.5060	1.5060	3.2032	3.2032
Si2	2.1856		3.2032	3.2032	1.5060	1.5060
H3	1.5060	3.2032		2.5155	3.7353	4.5033
H4	1.5060	3.2032	2.5155		4.5033	3.7353
H5	3.2032	1.5060	3.7353	4.5033		2.5155
H6	3.2032	1.5060	4.5033	3.7353	2.5155

picture of Disilene state 1 conformation 2

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
Si1	Si2	H5	119.241	Si1	Si2	H6	119.241
Si2	Si1	H3	119.241	Si2	Si1	H4	119.241
H3	Si1	H4	113.266	H5	Si2	H6	113.266

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at PBEPBE/3-21G Charges (e)

Number	Element	Mulliken
1	Si	0.090
2	Si	0.090
3	H	-0.045
4	H	-0.045
5	H	-0.045
6	H	-0.045

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	-32.020	0.178	0.000
y	0.178	-28.307	0.000
z	0.000	0.000	-29.877

Traceless
	x	y	z
x	-2.928	0.178	0.000
y	0.178	2.641	0.000
z	0.000	0.000	0.286

Polar
3z²-r²	0.572
x²-y²	-3.713
xy	0.178
xz	0.000
yz	0.000

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

	x	y	z
x	4.537	-0.629	0.000
y	-0.629	13.709	0.000
z	0.000	0.000	6.470

<r²> (average value of r²) Å²

<r²>	72.499
(<r²>)^1/2	8.515

Conformer 3 (C2V)

Jump to S1C1 S1C2

Energy calculated at PBEPBE/3-21G

	hartrees
Energy at 0K	-577.872479
Energy at 298.15K
HF Energy	-577.872479
Nuclear repulsion energy	69.182443

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 PBEPBE/3-21G

Mode Number	Symmetry	Frequency (cm^-1)	Scaled Frequency (cm^-1)	IR Intensities (km mol^-1)	Raman Act (Å⁴/u)	Dep P	Dep U
1	A₁	1932	1914	388.09	248.96	0.41	0.58
2	A₁	1404	1391	0.89	57.39	0.16	0.27
3	A₁	864	856	33.82	101.04	0.42	0.59
4	A₁	442	438	0.32	33.50	0.44	0.61
5	A₁	345	342	0.60	25.72	0.28	0.43
6	A₂	1092	1082	0.00	4.52	0.75	0.86
7	A₂	598	592	0.00	0.12	0.75	0.86
8	B₁	1053	1044	59.91	2.07	0.75	0.86
9	B₁	784	777	19.48	32.31	0.75	0.86
10	B₂	1906	1889	5.42	4.35	0.75	0.86
11	B₂	1039	1030	848.86	13.82	0.75	0.86
12	B₂	681	675	19.35	25.89	0.75	0.86

Unscaled Zero Point Vibrational Energy (zpe) 6070.1 cm^-1
Scaled (by 0.9909) Zero Point Vibrational Energy (zpe) 6014.9 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 PBEPBE/3-21G

A	B	C
2.39820	0.14451	0.14135

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

Geometric Data calculated at PBEPBE/3-21G

Point Group is C_2v

Cartesians (Å)

Atom	x (Å)	y (Å)	z (Å)
Si1	0.000	1.407	-0.089
Si2	0.000	-1.407	-0.089
H3	-1.047	0.000	-0.231
H4	1.047	0.000	-0.231
H5	0.000	1.351	1.473
H6	0.000	-1.351	1.473

Atom - Atom Distances (Å)

	Si1	Si2	H3	H4	H5	H6
Si1		2.8140	1.7598	1.7598	1.5624	3.1691
Si2	2.8140		1.7598	1.7598	3.1691	1.5624
H3	1.7598	1.7598		2.0946	2.4133	2.4133
H4	1.7598	1.7598	2.0946		2.4133	2.4133
H5	1.5624	3.1691	2.4133	2.4133		2.7014
H6	3.1691	1.5624	2.4133	2.4133	2.7014

picture of Disilene state 1 conformation 3

More geometry information
Calculated Bond Angles

atom1	atom2	atom3	angle	atom1	atom2	atom3	angle
Si1	Si2	H5	29.518	Si1	Si2	H6	87.936
Si2	Si1	H3	36.914	Si2	Si1	H4	36.914
H3	Si1	H4	73.046	H5	Si2	H6	58.418

Electronic energy levels

Charges, Dipole, Quadrupole and Polarizability
Charges from optimized geometry at PBEPBE/3-21G Charges (e)

Number	Element	Mulliken
1	Si	0.232
2	Si	0.232
3	H	-0.163
4	H	-0.163
5	H	-0.069
6	H	-0.069

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	0.985	0.985
CHELPG
AIM
ESP

Electric Quadrupole moment
Quadrupole components in D Å

Primitive
	x	y	z
x	-29.069	0.000	0.000
y	0.000	-32.599	0.000
z	0.000	0.000	-34.348

Traceless
	x	y	z
x	4.405	0.000	0.000
y	0.000	-0.891	0.000
z	0.000	0.000	-3.514

Polar
3z²-r²	-7.029
x²-y²	3.530
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	5.854	0.000	0.000
y	0.000	14.676	0.000
z	0.000	0.000	7.290

<r²> (average value of r²) Å²

<r²>	85.927
(<r²>)^1/2	9.270

All results from a given calculation for Si2H4 (Disilene)

using model chemistry: PBEPBE/3-21G

States and conformations

Conformer 1 (D2H)

Conformer 2 (C2H)

Conformer 3 (C2V)

All results from a given calculation for Si₂H₄ (Disilene)