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Calculated Proton Affinity

20 10 26 10 44
Name Species   Species Name
Acetylene C2H2 C2H3+ vinyl cation

Bonding changes

Bond type H-C changed by +2
Bond type C#C lost 1
Bond type C=C gained 1
Proton Affinities (kJ/mol)
Proton Affinities in kJ/mol
Methods with predefined basis sets
composite G4 621

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-pVDZ daug-cc-pVTZ
hartree fock HF 792 660 660 680 683 690 677 671 675 688 673 671 681 675 675 677 675 675 678 675
density functional LSDA                             611   627 611    
BLYP 751 645 645 660 664 668 648 641 644 663 640 640 652 643   643 641   643 641
B1B95 734 632 632 649 655 675 651 642 652 668 653 648 657 654 644 652 654 644 653 654
B3LYP 749 641 641 657 662 667 649 641 645 665 644 641 652 646 646 645 645 645 645 645
B3LYPultrafine   641     662 667 649 641   665 644 641 652 646   645 645   645 645
B3PW91 744 638 638 656 660 667 654 644 653 670 655 651 659 656   655 656   656 656
mPW1PW91 744 637 637 655 659 667 653 643 654 670 655 651 660 657   656 656   656 656
M06-2X 726 615 615 632 643 653 639 629 638 655 639 636 644 640   640 640   640 640
PBEPBE 741 636 636 652 655 664 647 637 648 666 647 643 654 649 639 647 647 639 647 647
PBEPBEultrafine   636     655 664 647 637   666 647 643 654 649   647 647   647 647
PBE1PBE 743 634 634 651 655 655 651 642 652 668 653 649 657 654   653 654   654 654
HSEh1PBE 744 635 635 652 656 665 651 641 651 668 652 648 657 653   653 653   653 653
TPSSh 748 645 645 662 667 671 658 651 657 673 657 653 663 658 658 658 657 657 659 657
wB97X-D 751 640 640 659 664 668 655 646 655 672 657 653 661 659 659 657 659 659 658 659
B97D3 756 655 655 672 675 680 664 658 661 678 660 657 667 662 661 660 661 661 661 661
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-pVDZ daug-cc-pVTZ
Moller Plesset perturbation MP2 701 589 589 600 625 648 635 612 634 641 627 634 636 631 629 627 629 627 627 629
MP2=FULL 701 589 589 600 625 648 635 612 634 641 627 634 636 633 629 628 632 628 628 632
MP3         643   649       645 653 654 649            
MP3=FULL         642   653                          
MP4   613     636       645   637 579 648 640   639 638      
MP4=FULL   613     636       645   636   648 642   640 641      
B2PLYP 735 624 624 638 643 656 640 625 639 655 637 637 645 639   637 638   637 638
B2PLYP=FULL 735 624 624 638 643 656 640 625 639 655 637 637 645 640   637 639   638 639
B2PLYP=FULLultrafine         643                       628      
Configuration interaction CID   622 622 638 645     635     650   657 653            
CISD   556 627 643 648     634     650   656 653            
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-pVDZ daug-cc-pVTZ
Quadratic configuration interaction QCISD   621 621 636 643 661 646 629 649 656 644 649 651 647   645 646      
QCISD(T)         637     626     640 645 649 643   641 641      
Coupled Cluster CCD   613 613 627 640 663 651 630 651 657 645 651 652 648   645 647      
CCSD         642 661 649 628 650 656 644 649 651 647 646 645 646      
CCSD=FULL         641         656 644 649 652 649 646 645 649      
CCSD(T)         636 659 646 626 647 652 640 645 649 643 641 641 641      
CCSD(T)=FULL         636           639 645 649 645 641 642 644 641    
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-pVDZ 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 693 699 671 675 669 668     674
density functional BLYP                 642
B1B95                 653
B3LYP 668 675 652 656 645 646     645
B3LYPultrafine                 645
B3PW91                 656
mPW1PW91                 656
M06-2X                 641
PBEPBE                 648
PBEPBEultrafine                 648
PBE1PBE                 654
HSEh1PBE                 653
TPSSh                 658
wB97X-D 673 680 656 659 651 651     658
B97D3                 661
Moller Plesset perturbation MP2 607 634 590 621 585 584     630
MP2=FULL                 630
B2PLYP                 639
B2PLYP=FULL                 639
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.