National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
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III.D.11.

Calculated Proton Affinity

Name Species   Species Name
Ethynyl radical C2H C2H2+ acetylene cation

Bonding changes

Bond type H-C changed by +1
Proton Affinities (kJ/mol)
Proton Affinities in kJ/mol
Methods with predefined basis sets
composite G2 734
G3 732
G3B3 721
G4 723
CBS-Q 725

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) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ cc-pV(T+d)Z
hartree fock HF 854 736 736 756   792 783 776 784 800 782 789 782 789 789
ROHF         828                    
density functional LSDA 852 726 726 751 748 756 741 731 738 758 743 739 737   739
SVWN   726     748   737                
BLYP 880 767 767 789 781 795 776 772 778 797 777 777     777
B1B95 868 759 759 832 794 795 780 768 781 797 781 782 777   782
B3LYP 885 771 771 795 798 803 784 781 788 810   790 781 786 790
B3LYPultrafine         798                 788  
B3PW91 876 762 762 789 795 801 789 780 786 803 788 788     788
mPW1PW91 875 763 760 788 798 804 790 783 787 804 791 791     791
M06-2X     780                        
PBEPBE 869 753 753 774 781 786 770 764 770 788 771 770     770
PBE1PBE         792                    
HSEh1PBE         793                    
TPSSh         797   789     805   793      
wB97X-D     770   804       794     798   797  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ cc-pV(T+d)Z
Moller Plesset perturbation MP2 940 788 788 818 818 833 819 799 813 824 816 809 809 807 809
MP2=FULL 940 788 788 818 817 832 818 799 813 822 816 810 810 808 810
MP3         831   847                
MP3=FULL         830   833                
MP4   787     821       818     812      
B2PLYP                       780      
Configuration interaction CID   787 787 814 823     808              
CISD   761 761 786 804     789              
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ cc-pV(T+d)Z
Quadratic configuration interaction QCISD   737 737 760 779 794 783 765 780 791 778 780     780
QCISD(T)         773           772 770      
Coupled Cluster CCD   789 789 818 826 841 829 810 824 835 827 821      
CCSD(T)         775           773 773 763 771 773
CCSD(T)=FULL         774             777 764 774  
STO-3G 3-21G 3-21G* 6-31G 6-31G* 6-31G** 6-31+G** 6-311G* 6-311G** 6-31G(2df,p) cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ cc-pV(T+d)Z

Proton Affinities in kJ/mol
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 750 787 742 778 743 742
density functional B3LYP 801 822 780 784 781 782
Moller Plesset perturbation MP2 831 835 809 809 808 808
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.