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

Geometry Comparison

Li2 (Lithium diatomic)


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

Experimental bond length is 2.673  Å

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Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM3 2.482
PM6 2.805
composite G2 2.767
G3 2.767
G3B3 2.714
G4 2.752
CBS-Q 2.767

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 cc-pCVDZ cc-pCVTZ
hartree fock HF 2.697 2.816 2.816 2.816 7.007 2.807 2.815 2.784 2.784 2.807 2.785 2.966 2.808 2.783 2.784 2.803 2.784 2.784 2.792 2.783
density functional LSDA 2.693 2.738 2.738 2.743 2.734 2.734 2.734 2.700 2.700 2.717   2.703 2.718 2.693   2.717 2.693   2.709 2.693
SVWN   2.966     3.545 2.734 2.966 2.700 2.700 2.717     2.718 2.693   2.717 2.693   2.709 2.693
BLYP 2.709 2.729 2.729 2.739 2.728 2.728 2.730 2.715 2.715 2.728   2.721 2.715 2.706   2.716     2.717 2.710
B1B95 2.680 2.739 2.739 2.748 2.741 2.741 2.743 2.715 2.715 2.739   2.719 2.734 2.714   2.732 2.714   2.725 2.714
B3LYP 2.689 2.725 2.725 2.733 2.723 2.723 2.725 2.705 2.705 2.721 2.701 2.966 2.712 2.698 2.692 2.713 2.699 2.697 2.709 2.700
B3LYPultrafine         2.723               2.712 2.698   2.713 2.699   2.709 2.700
B3PW91 2.701 2.768 2.768 2.770 2.761 2.761 2.762 2.737 2.737 2.753   2.737 2.753 2.731   2.752     2.746 2.732
mPW1PW91 2.697 2.766 2.766 2.768 2.759 2.759 2.761 2.737 2.737 2.752   2.736 2.752 2.732   2.750 2.731   2.745 2.732
M06-2X 2.655 2.744 2.744 2.729 2.966 2.721 2.724 2.693 2.693 2.720   2.699 2.723 2.692   2.721 2.691   2.712 2.690
PBEPBE 2.711 2.753 2.753 2.760 2.751 2.751 2.752 2.734 2.734 2.746 2.728 2.736 2.741 2.726   2.742 2.725   2.739 2.728
PBEPBEultrafine         2.751               2.741 2.726   2.742 2.726   2.739 2.728
PBE1PBE 2.694 2.758 2.758 2.761 3.809 2.753 2.755 2.732 2.732 2.747   2.731 2.745 2.726   2.744 2.726   2.738 2.727
HSEh1PBE 2.697 2.758 2.758 2.763 2.966 2.754 2.756 2.733 2.733 2.749   2.733 2.746 2.727   2.745 2.727   2.739 2.728
TPSSh         3.159   3.159             3.149            
Moller Plesset perturbation MP2 2.700 2.794 2.794 2.811 2.782 2.782 2.787 2.748 2.748 2.780   2.966 2.787 2.750 2.746 2.782 2.750 2.747 2.766 2.748
MP2=FULL 2.696 2.792 2.792 2.806 2.773 2.773 2.777 2.737 2.737 2.710   2.749 2.772 2.718 2.672 2.762 2.713 2.677 2.750 2.725
MP3         2.759   3.159                       2.740 2.728
MP3=FULL         3.159   3.159                          
MP4   2.752     2.748     2.712 2.712     2.713 2.746 2.719   2.744 2.718   2.726 2.718
MP4=FULL   2.750     2.739       2.702       2.730 2.686   2.724 2.679   2.711 2.696
B2PLYP         2.966                              
Configuration interaction CID   2.731 2.731 2.762 2.732     2.693                     2.710 2.702
CISD   2.738 2.738 2.771 2.734     2.693                     2.709 2.700
Quadratic configuration interaction QCISD   2.738 2.738 2.771 2.734 2.734 2.739 2.693 2.693 2.732   2.707 2.728 2.700   2.727 2.700   2.709 2.700
QCISD(T)         2.734     2.693       2.707 2.728 2.700   2.727 2.700   2.709 2.699
Coupled Cluster CCD   2.731 2.731 2.762 2.732 2.732 2.737 2.693 2.693 2.734   2.700 2.729 2.703   2.728 2.703   2.710 2.702
CCSD         2.734     2.693       2.707 2.728 2.700 2.698 2.727 2.700 2.699 2.709 2.700
CCSD=FULL         2.725             2.705 2.713 2.669 2.623 2.707 2.662 2.626 2.697 2.682
CCSD(T)   2.738     2.734 2.733 2.738 2.693 2.693   2.705 2.707 2.728 2.700 2.698 2.727 2.700 2.699 2.709 2.699
CCSD(T)=FULL         2.724             2.706 2.712 2.667 2.620 2.706 2.660 2.623 2.696 2.679

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 2.962 2.967 2.794 2.790 2.817 2.806
density functional B1B95 2.952 2.954        
B3LYP 2.945 2.947 2.748 2.743 2.721 2.722
Moller Plesset perturbation MP2 2.967 2.938 2.782 2.753 2.807 2.788
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
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