TABLE III.
Equilibrium structure of dimethyloxirane.a Distances are in Å, angles in degrees.
| Parameters | B3LYP/ SNSD |
B3LYP/ AVTZ |
CAM-B3LYP/ SNSD |
CAM-B3LYP/ AVTZ |
B2PLYP/ AVTZ |
MP2/ AVTZ |
best “cheap”b |
bestCC (TZ,QZ)/(CT)c |
|---|---|---|---|---|---|---|---|---|
| Bonds | ||||||||
| O1-C2 | 1.4402 | 1.4374 | 1.4295 | 1.4268 | 1.4410 | 1.4438 | 1.4369 | 1.4329 |
| C2-C3 | 1.4696 | 1.4658 | 1.4635 | 1.4596 | 1.4638 | 1.4637 | 1.4616 | 1.4611 |
| C2-C7 | 1.5060 | 1.5021 | 1.5007 | 1.4968 | 1.4998 | 1.4972 | 1.4970 | 1.4970 |
| C2-H6 | 1.0927 | 1.0881 | 1.0915 | 1.0870 | 1.0864 | 1.0866 | 1.0866 | 1.0864 |
| C5-H11 | 1.0941 | 1.0896 | 1.0930 | 1.0885 | 1.0883 | 1.0886 | 1.0886 | 1.0884 |
| C5-H12 | 1.0965 | 1.0920 | 1.0950 | 1.0905 | 1.0906 | 1.0905 | 1.0904 | 1.0902 |
| C5-H13 | 1.0958 | 1.0913 | 1.0943 | 1.0899 | 1.0898 | 1.0897 | 1.0895 | 1.0893 |
| MAEd | 0.0071 | 0.0030 | 0.0041 | 0.0013 | 0.0021 | 0.0021 | 0.0007 | |
| ∣MAX∣d | 0.0090 | 0.0051 | 0.0051 | 0.0061 | 0.0080 | 0.0109 | 0.0039 |
| Angles | ||||||||
| C2-O1-C3 | 61.36 | 61.31 | 61.58 | 61.53 | 61.05 | 60.91 | 61.14 | 61.31 |
| C3-C2-C7 | 123.13 | 123.22 | 122.92 | 122.97 | 122.91 | 122.40 | 122.55 | 122.44 |
| C3-C2-H6 | 116.69 | 116.67 | 116.71 | 116.7 | 116.67 | 116.55 | 116.68 | 116.71 |
| C2-C7-H8 | 110.82 | 110.87 | 110.60 | 110.64 | 110.58 | 110.13 | 110.27 | 110.23 |
| C2-C7-H9 | 110.52 | 110.50 | 110.60 | 110.57 | 110.48 | 110.52 | 110.43 | 110.51 |
| C2-C7-H10 | 110.58 | 110.55 | 110.55 | 110.53 | 110.50 | 110.45 | 110.38 | 110.52 |
| H4-C3-C2-O1 | 102.03 | 102.1 | 102.14 | 102.23 | 102.03 | 102.06 | 101.91 | 102.18 |
| H8-C7-C2-C3 | 24.33 | 24.51 | 24.45 | 24.56 | 24.38 | 24.34 | 23.50 | 24.17 |
| H9-C7-C2-C3 | −96.24 | −96.06 | −96.1 | −95.97 | −96.13 | −96.10 | −96.94 | −96.23 |
| H10-C7-C2-C3 | 144.34 | 144.57 | 144.31 | 144.48 | 144.34 | 144.11 | 143.37 | 144.01 |
| MAEd | 0.21 | 0.27 | 0.20 | 0.24 | 0.19 | 0.13 | 0.28 | |
| ∣MAX∣d | 0.69 | 0.78 | 0.47 | 0.53 | 0.47 | 0.39 | 0.71 |
a
By symmetry, we have the following relationships: O1-C2 = O1-C3; C2-C7 = C3-C5; C2-H6 = C3-H4; C5-H11 = C7-H8; C5-H12 = C7-H9; C5-H13 = C7-H10; C3-C2-C7 = C2-C3-C5; C3-C2-H6 = C2-C3-H4; H4-C3-C2-O1 = H6-C2-C3-O1.
b
Best-estimated equilibrium structure obtained by means of the “cheap” scheme (Eq. (3)).
c
Best-estimated “bestCC” equilibrium structure (Eq. (1)) using the cc-pVTZ and cc-pVQZ basis sets for the CBS extrapolation and cc-pCVTZ for the core-correlation correction.
d
Mean absolute error (MAE) and maximum absolute deviations (∣MAX∣) with respect to the best-estimated (bestCC) parameters.