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Calculated Proton Affinity

20 10 26 10 44
Name Species   Species Name
Carbon diatomic C2 C2H+ Ethynyl cation

Bonding changes

Bond type H-C gained 1
Proton Affinities (kJ/mol)
Proton Affinities in kJ/mol
Methods with predefined basis sets
semi-empirical PM3  
composite G4 393

Proton Affinities in kJ/mol
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 daug-cc-pVTZ
hartree fock HF 488 353 353 358 345 351 340 337 345 349   352 330 347 348 326 346 348 1044
density functional LSDA 519 401 401 409 395 400 386 386 394 401     383 397   379 396    
BLYP 493 393 393 401   393 376 380 387 393     374 389          
B1B95 496 387 387 396 384 390 377 376 384 391     371 388 389 374 387 678  
B3LYP 498 392 392 399 350 390 376 378 385 390   387 371 387 389 366 386 388  
B3LYPultrafine   392     384 390 376 378         371 387     386    
B3PW91 497 388 388 397 383 388 377 377 385 389     371 387          
mPW1PW91 496 385 385 394 380 385 374 375 382 386     368 384          
M06-2X     769   397                            
PBEPBE 495 388 388 398 385 391 376 378 386 391     374 387 389     388  
PBE1PBE         378                            
HSEh1PBE   385     379   487             382          
TPSSh         376   370     643       380          
wB97X-D     782   808   803   807     809 803 812     812    
B97D3                                      
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 daug-cc-pVTZ
Moller Plesset perturbation MP2 553 392 392 395 380 396 382 368 386 396   393 372 392   364 390 635  
MP2=FULL 553 392 392 395 382 399 385 370 388 400     373 403     403 640  
MP3         656                            
MP3=FULL         375   380                        
MP4   405     385       391         395          
B2PLYP         385                 389          
Configuration interaction CID   409 409 410 379     368                      
CISD   409 409 408 379     368                      
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 daug-cc-pVTZ
Quadratic configuration interaction QCISD   422 422 426 401 417 404 387 405 412     392 408          
QCISD(T)         419               414 421     419    
Coupled Cluster CCD       433 399 415 403 385 403 410     390 407   382 406    
CCSD         399                            
CCSD(T)         423               418 424   409 422    
CCSD(T)=FULL         424                            
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 daug-cc-pVTZ

Proton Affinities in kJ/mol
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD cc-pVTZ-PP aug-cc-pVTZ-PP Def2TZVPP
hartree fock HF 309 296 328 321 346 346     1044
density functional B3LYP 345   357 350 381 381     778
PBEPBE                 867
Moller Plesset perturbation MP2 350 341 357 348 375 374     612
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.