National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 19April 2018
NIST Standard Reference Database 101
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III.D.11.

Calculated Proton Affinity

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
composite G2 389
G3 383
G3B3 640
G4 393
CBS-Q 386

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) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
hartree fock HF 488 353 353 358 345 351 340 337 345 349 352 1044 330 347 348 326 346 348
density functional LSDA 519 425 401 409 395 400 386 386 394 401     383 437   379 396  
BLYP 493 393 393 401 675 393 376 380 387 393     374 389        
B1B95 496 387 459 396 384 390 377 376 384 391     459 388 389 374 387 678
B3LYP 498 392 392 399 350 390 376 378 385 390 387 778 371 387 389 366 386 388
B3LYPultrafine   392     384 485 376 378         469 387     386  
B3PW91 497 470 388 397 383 388 377 377 385 389     371 387        
mPW1PW91 496 385 385 394 380 385 374 375 382 386     368 384        
M06-2X     769   492                          
PBEPBE 495 388 388 398 385 391 376 378 386 390   867 374 387 389     388
PBE1PBE         378                          
HSEh1PBE   396     379   487             382        
TPSSh         376   466     643       380        
wB97X-D     688   808   803   807   809   803 812     812  
B97D3                           858     868  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Moller Plesset perturbation MP2 553 392 392 395 380 396 382 368 386 396 393 612 372 392   364 390 605
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) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ
Quadratic configuration interaction QCISD   422 422 426 401 417 404 387 405 412     392 408        
QCISD(T)         419               414 421     419  
Coupled Cluster CCD     672 433 399 415 403 385 403 410     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) TZVP Def2TZVPP cc-pVDZ cc-pVTZ cc-pVQZ aug-cc-pVDZ aug-cc-pVTZ aug-cc-pVQZ

Proton Affinities in kJ/mol
Methods with effective core potentials (select basis sets)
daug-cc-pVDZ daug-cc-pVTZ daug-cc-pVQZ Sadlej_pVTZ CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF         309 296 328 321 346 346
density functional B3LYP         345 651 357 350 381 381
Moller Plesset perturbation MP2         350 341 357 348 375 374
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.