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IV.D.1. (XII.C.1.)

Geometry Comparison

C2H2 (Acetylene)


distance is atom 1 (C) to atom 2 (C)

Experimental bond length is 1.203  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM3 1.190
composite G2 1.185
G3 1.185
G3B3 1.205
G4 1.199
CBS-Q 1.188

Calculated bond length in 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) 6-311+G(3df,2pd) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ cc-pCVDZ cc-pCVTZ Sadlej_pVTZ
hartree fock HF 1.168 1.188 1.188 1.194 1.185 1.186 1.189 1.183 1.182 1.181 1.180 1.180 1.181 1.192 1.180 1.179 1.192 1.180 1.179     1.192
density functional LSDA 1.207 1.208 1.208 1.216 1.211 1.211 1.213 1.202 1.202 1.205 1.200 1.200 1.202 1.215 1.200 1.199 1.215 1.200 1.200      
SVWN 1.207 1.208 1.208 1.216 1.211 1.211 1.213 1.202 1.202 1.205 1.200 1.200 1.202 1.215 1.200 1.199 1.215 1.200 1.200      
BLYP 1.213 1.213 1.213 1.220 1.215 1.215 1.218 1.208 1.207 1.209 1.206 1.206 1.208 1.220 1.205 1.205 1.220 1.206 1.205      
B1B95 1.199 1.203 1.203 1.210 1.203 1.204 1.207 1.198 1.198 1.198 1.194 1.194 1.196 1.208 1.194 1.193 1.207 1.194 1.194      
B3LYP 1.201 1.204 1.204 1.211 1.205 1.205 1.208 1.199   1.199 1.196 1.196 1.198 1.210 1.196 1.195 1.210 1.196 1.196     1.214
B3LYPultrafine 1.201 1.204 1.204 1.211 1.205 1.205 1.208 1.199 1.198 1.199 1.196 1.196 1.198 1.210 1.196 1.195 1.210 1.196 1.196      
B3PW91   1.205 1.205 1.211 1.206 1.206 1.208 1.200   1.200 1.197 1.197 1.199 1.210 1.197 1.196 1.210 1.197 1.196      
mPW1PW91   1.203   1.210 1.203 1.204 1.206 1.198 1.197 1.198 1.195 1.195 1.197 1.208 1.195 1.194 1.208 1.195 1.195      
M06-2X 1.193 1.202 1.202 1.207 1.202 1.202 1.205 1.197 1.196 1.195 1.194 1.194 1.196 1.207 1.194 1.193 1.206 1.194 1.193      
PBEPBE   1.214     1.216 1.216 1.219 1.209 1.209 1.210 1.207 1.207 1.209 1.220 1.207 1.206   1.207 1.207     1.225
PBEPBEultrafine 1.211 1.214 1.214 1.221 1.216 1.216 1.219 1.209 1.209 1.210 1.207 1.207 1.209 1.220 1.207 1.206 1.220 1.207 1.207      
PBE1PBE 1.197 1.204 1.204 1.210 1.204 1.205 1.207 1.199 1.199 1.199 1.196 1.197 1.198 1.209 1.196 1.196 1.209 1.197 1.196      
HSEh1PBE 1.197 1.204 1.204 1.210 1.204 1.205 1.207 1.199 1.198 1.199 1.196 1.196 1.198 1.209 1.196 1.195 1.209 1.196 1.196      
TPSSh         1.189   1.193               1.183              
Moller Plesset perturbation MP2   1.222 1.222 1.232 1.218 1.219 1.221 1.216 1.215 1.212 1.211 1.211 1.211 1.230 1.211 1.209 1.231 1.212 1.209 1.228 1.210 1.234
MP2=FULL 1.218 1.222 1.222 1.232 1.216 1.217 1.219 1.215   1.209 1.209 1.209 1.210 1.229 1.207 1.206 1.231 1.208 1.206 1.227 1.208  
MP3 1.205 1.210 1.210 1.219 1.206 1.207 1.209 1.204 1.204 1.200 1.199 1.199 1.199 1.218 1.200 1.196 1.220 1.200 1.197      
MP3=FULL         1.182   1.187                              
MP4 1.209 1.222 1.222 1.232 1.220 1.220 1.223 1.219 1.218 1.213 1.213 1.213 1.214 1.231 1.213 1.211 1.233 1.214 1.211      
MP4=FULL 1.209 1.222 1.222 1.232 1.218 1.219 1.221 1.218 1.217 1.210 1.211 1.211 1.213 1.230 1.210 1.208 1.232 1.210 1.208      
B2PLYP=FULLultrafine         1.209                                  
Configuration interaction CID 1.203 1.208 1.208 1.217 1.203 1.203 1.205 1.201 1.200 1.196 1.194 1.194 1.196 1.213 1.195 1.191 1.214 1.195 1.192      
CISD 1.203   1.210 1.219 1.205   1.207 1.202 1.201 1.197 1.196 1.195 1.198 1.215 1.196 1.193 1.216 1.196 1.193      
Quadratic configuration interaction QCISD 1.213 1.218 1.218 1.228 1.213   1.215 1.211 1.210 1.205 1.204 1.204 1.206 1.224 1.204 1.201 1.225 1.205 1.201      
QCISD(T) 1.213 1.221 1.221 1.231 1.217 1.218 1.220 1.216 1.215 1.210 1.210 1.210 1.211 1.229 1.210 1.207 1.230 1.211 1.207      
QCISD(TQ) 1.215 1.221 1.221 1.231 1.217 1.218 1.220 1.215 1.214 1.210 1.209     1.229 1.209 1.206 1.230 1.210        
Coupled Cluster CCD 1.213 1.215 1.215 1.225 1.209 1.210 1.212 1.207 1.206 1.202 1.201 1.201 1.202 1.221 1.201 1.198 1.222 1.202 1.198      
CCSD 1.213 1.217 1.217 1.227 1.212 1.212 1.214 1.210 1.209 1.204 1.203 1.203 1.205 1.223 1.203 1.200 1.224 1.204 1.200      
CCSD=FULL 1.212 1.217 1.217 1.227 1.210 1.211 1.213 1.209 1.208 1.201 1.201 1.201 1.204 1.222 1.199 1.198 1.223 1.200 1.197      
CCSD(T) 1.213 1.221 1.221 1.231 1.217 1.218 1.220 1.215 1.215 1.210 1.209 1.209 1.210 1.229 1.210 1.207 1.230 1.210 1.207 1.227 1.209  
CCSD(T)=FULL 1.213 1.221 1.221 1.231 1.216 1.216 1.219 1.215 1.214 1.207 1.207 1.207 1.209 1.228 1.206 1.204 1.229 1.206 1.204 1.226 1.207  

Calculated bond length in Å
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 1.227 1.221 1.201 1.190 1.202 1.201
density functional LSDA 1.259 1.255 1.233 1.224 1.227 1.227
SVWN 1.259 1.255 1.233 1.224 1.227 1.227
BLYP 1.257 1.252 1.231 1.220 1.233 1.233
B1B95 1.248 1.244 1.219 1.210 1.218 1.218
B3LYP 1.248 1.243 1.222 1.211 1.222 1.222
B3LYPultrafine 1.248 1.243 1.222 1.211 1.222 1.222
B3PW91 1.247 1.242 1.221 1.211 1.221 1.221
mPW1PW91 1.245 1.240 1.219 1.209 1.219 1.219
M06-2X 1.246 1.242 1.216 1.207 1.217 1.217
PBEPBE 1.257 1.253 1.231 1.222 1.232 1.232
PBEPBEultrafine 1.257 1.253 1.231 1.222 1.232 1.232
PBE1PBE 1.246 1.241 1.220 1.210 1.220 1.220
HSEh1PBE 1.246 1.242 1.220 1.211 1.220 1.220
Moller Plesset perturbation MP2 1.275 1.257 1.243 1.224 1.246 1.245
MP2=FULL 1.275 1.257 1.243 1.224 1.246 1.245
MP3 1.261 1.245 1.230 1.213 1.231 1.230
MP4 1.273 1.257 1.242 1.225 1.244 1.243
MP4=FULL 1.273 1.257 1.242 1.225 1.244 1.243
Configuration interaction CID 1.259 1.241 1.227 1.209 1.229 1.228
CISD 1.261 1.243 1.229 1.210 1.231 1.230
Quadratic configuration interaction QCISD 1.271 1.251 1.238 1.219 1.240 1.239
QCISD(T) 1.274 1.256 1.242 1.224 1.243 1.242
QCISD(TQ) 1.274 1.256 1.242 1.223 1.244 1.243
Coupled Cluster CCD 1.268 1.248 1.236 1.216 1.237 1.236
CCSD 1.270 1.250 1.238 1.218 1.239 1.238
CCSD=FULL 1.270 1.250 1.238 1.218 1.239 1.238
CCSD(T) 1.274 1.256 1.242 1.223 1.243 1.242
CCSD(T)=FULL 1.274 1.256 1.242 1.223 1.243 1.242
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
Please use the error report form to report problems.