III.G.1.a.

Comparison of levels of theory for Si-O

Click on an entry for a histogram of the values.
The subscript refers to how many bonds of that type have been calculated.

average calculated bond lengths (Å)

Methods with predefined basis sets
semi-empirical	AM1	1.5760 2
	PM3	1.4830 5
	PM6	1.2516 5
composite	G2	1.5100 5
	G3	1.5100 5
	G3B3	1.5368 5
	CBS-Q	1.5104 5

average calculated bond lengths (Å)

Methods with standard basis sets
		STO-3G	3-21G	3-21G*	6-31G	6-31G*	6-31G**	6-31+G**	6-311G*	6-311G**	6-31G(2df,p)	6-311+G(3df,2p)	TZVP	cc-pVDZ	cc-pVTZ	cc-pVQZ	aug-cc-pVDZ	aug-cc-pVTZ	aug-cc-pVQZ	cc-pV(T+d)Z	cc-pCVDZ	cc-pCVTZ
hartree fock	HF	1.5303 5	1.5915 5	1.5194 5	1.6160 5	1.5100 5	1.5100 5	1.5115 5	1.5043 5	1.5042 5	1.5008 5	1.4748 3	1.5158 5	1.5327 5	1.5069 5	1.5008 5	1.5337 5	1.5047 5	1.5140 3	1.4753 3	1.5033 1	1.4784 1
density functional	LSDA	1.5747 5	1.5751 5	1.5457 5	1.6104 5	1.5368 5	1.5368 5	1.5378 5	1.5310 5	1.5310 5	1.5232 5			1.5569 5	1.5303 5	1.5376 2	1.5566 5	1.5394 2	1.5105 1
	SVWN		1.5953 5			1.5248 4		1.5378 5
	BLYP	1.5922 5	1.6138 5	1.5643 5	1.6312 5	1.5558 5	1.5558 5	1.5572 5	1.5508 5	1.5508 5	1.5422 5			1.5756 5	1.5497 5		1.5633 3
	B1B95	1.5653 5	1.5702 5	1.5415 5	1.6069 5	1.5300 5	1.5315 5	1.5327 5	1.5261 5	1.5261 5	1.5203 5			1.5526 5	1.5255 5	1.5391 2	1.5498 4	1.5568 1	1.5319 2
	B3LYP	1.5714 5	1.5954 5	1.5461 5	1.6127 5	1.5368 5	1.5368 5	1.5386 5	1.5318 5	1.5552 2	1.5246 5	1.5099 3	1.5417 5	1.5572 5	1.5318 5	1.5342 3	1.5574 5	1.5293 5	1.5299 3	1.5095 3	1.5378 1	1.5121 1
	B3LYPultrafine					1.5368 5
	B3PW91	1.5865 2	1.5941 5	1.5447 5	1.6103 5	1.5344 5	1.5344 5	1.5354 5	1.5291 5	1.5513 2	1.5229 5			1.5552 5	1.5293 5		1.5415 3
	mPW1PW91	1.5824 2	1.5905 5	1.5655 2	1.6070 5	1.5308 5	1.5308 5	1.5320 5	1.5254 5	1.5254 5	1.5196 5			1.5518 5	1.5259 5		1.5378 3
	M06-2X					1.5242 5
	PBEPBE	1.6041 2	1.6119 5	1.5837 2	1.6544 2	1.5524 5	1.5524 5	1.5533 5	1.5469 5	1.5469 5	1.5398 5	1.5267 3		1.5731 5	1.5464 5	1.5558 2		1.5345 3	1.5486 2	1.5270 1
	PBEPBEultrafine					1.5389 3
	HSEh1PBE					1.5320 5
Moller Plesset perturbation	MP2FC	1.5907 2	1.5823 5	1.5476 4	1.6094 5	1.5487 5	1.5487 5	1.5526 5	1.5385 5	1.5385 5	1.5376 5		1.5545 5	1.5715 4	1.5432 5	1.5451 3	1.5778 5	1.5516 3	1.5427 3	1.5238 3	1.5591 1	1.5275 1
	MP2FU	1.5911 2	1.5825 5	1.5603 2	1.6063 2	1.5482 5	1.5483 5	1.5520 5	1.5380 5	1.5581 2	1.5520 2			1.5708 5	1.5586 2	1.5385 3	1.5648 3		1.5400 2	1.5193 3	1.5588 1	1.5243 1
	MP3					1.5290 5
	MP4		1.5692 2			1.5644 5			1.5574 1	1.5706 2					1.5550 5
	B2PLYP					1.5408 5		1.5429 5
Configuration interaction	CID		1.6161 2	1.5580 1	1.5626 1	1.5276 5			1.5325 3
Configuration interaction	CISD		1.6221 2	1.5581 1	1.6346 2	1.5296 5			1.5486 2
Quadratic configuration interaction	QCISD		1.6129 5	1.5813 2	1.6657 2	1.5436 5	1.5705 2	1.5454 5	1.5317 5	1.5317 5	1.5544 2			1.5666 5	1.5333 5					1.5136 1
Quadratic configuration interaction	QCISD(T)					1.5492 5			1.5278 1					1.6010 2	1.5625 2		1.5995 2	1.5587 2
Coupled Cluster	CCD		1.6091 2	1.5584 1	1.6055 2	1.5344 5	1.5632 2	1.5619 2	1.5371 3	1.5513 2	1.5501 2			1.5556 5	1.5540 2		1.5898 2	1.5505 2			1.5338 1	1.5048 1
	CCSD					1.5370 5			1.5136 1
	CCSD(T)		1.5966 1			1.5301 3	1.5301 3	1.5393 1	1.5250 1	1.5250 1		1.5199 1		1.5974 2	1.5382 5		1.5967 2	1.5563 2		1.5189 1	1.5532 1	1.5201 1
	CCSD(T)=FULL					1.5590 3								1.5555 1	1.5243 1						1.5528 1	1.5173 1

average calculated bond lengths (Å)

Methods with effective core potentials (select basis sets)
		CEP-31G	CEP-31G*	CEP-121G	CEP-121G*	LANL2DZ	SDD
hartree fock	HF	1.6100 5	1.5161 5	1.6108 5	1.5172 5	1.5822 5	1.6012 5
density functional	B1B95	1.5859 3	1.5252 3
density functional	B3LYP	1.6100 5	1.5429 5	1.6103 5	1.5444 5	1.5846 5	1.6012 5
Moller Plesset perturbation	MP2FC	1.6163 5	1.5556 5	1.6200 4	1.5570 5	1.5924 5	1.6077 5

For descriptions of the methods (AM1, HF, MP2, ...) and basis sets (3-21G, 3-21G*, 6-31G, ...) see the glossary in section I.C. Predefined means the basis set used is determined by the method.