return to home page

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

Geometry Comparison

As2 (Arsenic diatomic)


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

Experimental bond length is 2.103  Å

Display Options
Switch to bar chart display
Calculated bond length in Å
Methods with predefined basis sets
semi-empirical PM6 1.934
composite G2 2.026
G3 2.050
G3B3 2.124
G4 2.115
CBS-Q 2.027

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) TZVP cc-pVDZ cc-pVTZ aug-cc-pVDZ aug-cc-pVTZ
hartree fock HF 1.979 2.121 2.065 2.086 2.049 2.049 2.055 2.064 2.064 2.032 2.063 2.061 2.061 2.065 2.061
density functional LSDA 1.980 2.097 2.097 2.116 2.084 2.084 2.090 2.097 2.097 2.058   2.099 2.090 2.100 2.090
BLYP 2.004 2.192 2.138 2.161 2.127 2.127 2.133 2.142 2.142 2.098   2.142 2.135    
B1B95 1.992 2.089 2.089 2.110 2.074 2.074 2.080 2.090 2.090 2.052   2.088 2.084 2.090 2.084
B3LYP 1.997 2.163 2.110 2.132 2.097 2.097 2.103 2.112 2.112 2.072 2.110 2.112 2.105 2.113 2.105
B3LYPultrafine         2.097                   2.114
B3PW91 1.997 2.157 2.102 2.122 2.086 2.086 2.092 2.101 2.101 2.063   2.100 2.095    
mPW1PW91 1.994 2.152 2.097 2.116 2.080 2.080 2.086 2.095 2.095 2.058   2.094 2.089 2.096 2.089
PBEPBE 1.999 2.183 2.126 2.145 2.110 2.110 2.116 2.126 2.126 2.083   2.125 2.119 2.126 2.119
PBE1PBE         2.080                    
TPSSh         2.086   2.092           2.096    
Moller Plesset perturbation MP2 2.106 2.281 2.159 2.223 2.152 2.152 2.157 2.166 2.166 2.108 2.144 2.156 2.127 2.159 2.128
MP2=FULL 2.105 2.281 2.156 2.220 2.142 2.142 2.147 2.154 2.154 2.078   2.153 2.120 2.157 2.114
MP3         2.106   2.108                
MP3=FULL         2.100   2.106                
MP4   2.248     2.148       2.164       2.133    
B2PLYP                         2.122    
Configuration interaction CID   2.180 2.102 2.140 2.094     2.105              
CISD   2.183 2.104 2.142 2.096     2.107              
Quadratic configuration interaction QCISD   2.217 2.128 2.169 2.119 2.119 2.125 2.131 2.131 2.082   2.124 2.099 2.127 2.098
QCISD(T)         2.137             2.141 2.117    
Coupled Cluster CCD   2.210 2.122 2.164 2.114 2.114 2.119 2.124 2.124 2.077   2.118 2.093 2.121 2.092
CCSD         2.117             2.122 2.097    
CCSD(T)         2.136             2.140 2.116 2.144 2.116
CCSD(T)=FULL         2.129             2.138 2.111 2.142 2.105

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 2.116   2.116   2.138 2.114
density functional B3LYP 2.169   2.169   2.193 2.164
Moller Plesset perturbation MP2 2.283   2.283   2.303 2.268
Values that are outliers may reflect incorrect atom numbering for different levels of theory.
Please use the error report form to report problems.