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

Geometry Comparison

Se2 (Selenium diatomic)


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

Experimental bond length is 2.166  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM3 2.118
PM6 2.211
composite G2 2.140
G3B3 2.216
G4 2.205
CBS-Q 2.142

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) TZVP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 2.158 2.270 2.141 2.223 2.140 2.140 2.141 2.149 2.149 2.102 2.137 2.150 2.145 2.138 2.136 2.147 2.138 2.136
ROHF 2.153 2.264 2.138 2.216 2.137 2.137 2.139 2.147 2.147 2.100     2.142 2.136   2.144    
density functional LSDA 2.201 2.294 2.163 2.262 2.173 2.173 2.174 2.180 2.180 2.127     2.177 2.168   2.180 2.167  
SVWN   2.299     2.170   2.174                      
BLYP 2.236 2.354 2.216 2.325 2.227 2.227 2.228 2.237 2.237 2.175     2.236 2.225        
B1B95 2.196 2.163 2.163 2.258 2.166 2.166 2.166 2.176 2.176 2.124     2.173 2.165 2.163 2.174 2.165 2.163
B3LYP 2.211 2.321 2.186 2.286 2.194 2.194 2.194 2.202 2.202 2.147   2.202 2.201 2.190 2.188 2.201 2.190 2.188
B3LYPultrafine         2.194                       2.198  
B3PW91 2.203 2.309 2.173 2.268 2.176 2.176 2.177 2.185 2.185 2.132     2.183 2.174        
mPW1PW91 2.197 2.302 2.167 2.260 2.169 2.169 2.169 2.178 2.178 2.126     2.175 2.167        
M06-2X         2.158                          
PBEPBE 2.221 2.335 2.195 2.299 2.200 2.200 2.200 2.206 2.206 2.153     2.208 2.199   2.209 2.199  
PBE1PBE         2.168                          
HSEh1PBE         2.168                          
TPSSh         2.189   2.190             2.185        
Moller Plesset perturbation MP2 2.252 2.421 2.209 2.382 2.220 2.220 2.221 2.231 2.231 2.155   2.219 2.218 2.173 2.160 2.223   2.158
MP2=FULL 2.252 2.421 2.208 2.383 2.213 2.213 2.214 2.225 2.225 2.137     2.216 2.168 2.159 2.222    
ROMP2   2.390 2.194 2.353 2.206 2.206 2.209 2.219 2.219 2.146     2.202 2.182   2.214    
MP3         2.209   2.222                      
MP3=FULL         2.216   2.216                      
MP4   2.401     2.229       2.241 2.147       2.185        
B2PLYP         2.204                 2.201        
Configuration interaction CID   2.359 2.178 2.313 2.186     2.191                    
CISD   2.363 2.179 2.318 2.188     2.194                    
Quadratic configuration interaction QCISD 2.220 2.398 2.200 2.354 2.209 2.209 2.209 2.217 2.217 2.147     2.207 2.182        
QCISD(T)         2.227               2.227 2.202   2.231 2.201  
Coupled Cluster CCD 2.219 2.390 2.196 2.344 2.204 2.204 2.205 2.211 2.211 2.143     2.202 2.176   2.205    
CCSD         2.208                          
CCSD(T)         2.227   2.203           2.226 2.201   2.230 2.200  
CCSD(T)=FULL         2.220                          

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 2.234   2.234   2.270 2.234
ROHF 2.228   2.228   2.264 2.228
density functional B1B95 2.281          
B3LYP 2.299   2.299   2.336 2.297
Moller Plesset perturbation MP2 2.389   2.389   2.431 2.382
ROMP2 2.371   2.371   2.401 2.362
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
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