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III.G.1.a.

Comparison of levels of theory for Se-Se


Click on an entry for a histogram of the values.
The subscript refers to how many bonds of that type have been calculated.
average calculated bond lengths (Å)
Methods with predefined basis sets
semi-empirical PM3 2.1420
3
PM6 2.2034
4
composite G2 2.1475
4
G3B3 2.2244
4
G4 2.2138
4
CBS-Q 2.1499
4

average calculated bond lengths (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
hartree fock HF 2.1646
4
2.2766
4
2.1477
4
2.2317
4
2.1486
7
2.1475
4
2.1490
4
2.1583
4
2.1583
4
2.1098
4
2.1366
1
2.1595
4
2.1531
4
2.1478
4
2.1456
4
2.1564
4
2.1508
3
2.1452
4
ROHF 2.1528
1
2.2636
1
2.1375
1
2.2160
1
2.1985
2
2.1370
1
2.1388
1
2.1466
1
2.1466
1
2.0997
1
    2.1418
1
2.1360
1
  2.1442
1
   
density functional LSDA 2.2088
4
2.1966
2
2.1309
2
2.2691
4
2.1804
4
2.1804
4
2.1804
4
2.1883
4
2.1883
4
2.1339
4
    2.1910
3
2.1763
4
2.1841
2
2.1874
4
2.1785
3
2.1829
2
SVWN   2.3049
4
    2.1704
1
  2.1804
4
                     
BLYP 2.2445
4
2.3256
3
2.2239
4
2.3321
4
2.2650
3
2.2650
3
2.2352
4
2.2781
3
2.2781
3
2.1845
4
    2.2457
4
2.2343
4
       
B1B95 2.2013
4
2.2023
4
2.1691
4
2.2631
4
2.1749
3
2.1722
4
2.1724
4
2.1836
4
2.1836
4
2.1295
4
    2.1801
4
2.1715
4
2.1732
3
2.1792
4
2.1743
3
2.2170
2
B3LYP 2.2189
4
2.3276
4
2.1940
4
2.2933
4
2.2017
4
2.2017
4
2.2018
4
2.2118
4
2.2118
4
2.1547
4
  2.2122
4
2.2099
4
2.1997
4
2.1975
4
2.2096
4
2.1986
4
2.1967
4
B3LYPultrafine         2.2054
3
                      2.2062
4
 
B3PW91 2.2112
4
2.3147
4
2.1799
4
2.2753
4
2.1838
4
2.1838
4
2.1836
4
2.1935
4
2.1935
4
2.1395
4
    2.1915
4
2.1821
4
       
mPW1PW91 2.2047
4
2.3072
4
2.1734
4
2.2669
4
2.1762
4
2.1762
4
2.1762
4
2.1860
4
2.1860
4
2.1331
4
    2.1836
4
2.1749
4
       
M06-2X         2.1668
4
                         
PBEPBE 2.2286
4
2.3411
4
2.2016
4
2.3053
4
2.2073
4
2.2073
4
2.2068
4
2.2216
3
2.2216
3
2.1601
4
    2.2165
4
2.2072
4
2.2154
2
2.2066
2
2.1968
2
2.2139
2
PBE1PBE         2.1749
4
                         
HSEh1PBE         2.1812
3
                         
TPSSh         2.2222
4
  2.2222
4
            2.2232
4
       
Moller Plesset perturbation MP2 2.2678
3
2.4290
4
2.2099
4
2.3872
4
2.2208
4
2.2208
4
2.2213
4
2.2319
4
2.2319
4
2.1562
4
  2.2208
4
2.2189
4
2.1727
1
2.1602
1
2.2242
4
  2.1579
1
MP2=FULL 2.2677
3
2.4297
4
2.2083
4
2.3881
4
2.2138
4
2.2138
4
2.2144
4
2.2258
4
2.2258
4
2.1382
4
    2.2169
4
2.1676
1
2.1590
1
2.2121
2
   
ROMP2   2.3898
1
2.1940
1
2.3531
1
2.2062
1
2.2062
1
2.2091
1
2.2191
1
2.2191
1
2.1462
1
    2.2023
1
2.1823
1
  2.2142
1
   
MP3         2.2128
3
  2.2395
4
                     
MP3=FULL         2.2341
4
  2.2350
4
                     
MP4   2.3979
4
    2.2261
4
      2.2389
4
2.1465
1
      2.2057
3
       
B2PLYP         2.2087
4
                2.2321
4
       
Configuration interaction CID   2.3599
3
2.1851
3
2.3171
3
2.1890
4
    2.2008
3
                   
CISD   2.3638
3
2.1867
3
2.3217
3
2.1907
4
    2.2031
3
                   
Quadratic configuration interaction QCISD 2.2197
1
2.3820
4
2.1983
4
2.3396
4
2.2075
4
2.2075
4
2.2142
3
2.2170
4
2.2170
4
2.1487
4
    2.2063
4
2.1837
4
       
QCISD(T)         2.2291
3
              2.2293
3
2.2066
3
  2.2350
3
2.2010
1
 
Coupled Cluster CCD 2.2190
1
2.3748
4
2.1948
4
2.3318
4
2.2037
4
2.2037
4
2.2094
3
2.2119
4
2.2119
4
2.1447
4
    2.2018
4
2.1838
3
  2.2118
3
   
CCSD         2.2064
4
                         
CCSD(T)         2.2139
2
  2.2033
1
          2.2211
4
2.1994
4
  2.2274
4
2.2004
1
 
CCSD(T)=FULL         2.2219
3
                         

average calculated bond lengths (Å)
Methods with effective core potentials (select basis sets)
CEP-31G CEP-31G* CEP-121G CEP-121G* LANL2DZ SDD
hartree fock HF 2.2474
3
  2.2474
3
  2.2790
4
2.2442
4
ROHF 2.2276
1
  2.2276
1
  2.2645
1
2.2275
1
density functional B1B95 2.2812
1
         
B3LYP 2.3080
4
  2.3080
4
  2.3442
4
2.3066
4
Moller Plesset perturbation MP2 2.3948
4
  2.3948
4
  2.4412
4
2.3872
4
ROMP2 2.3710
1
  2.3710
1
  2.4009
1
2.3623
1
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.