TABLE II.
Equilibrium structure of methyloxirane. Distances are in Å, angles in degrees.
| Parameters | B3LYP/ SNSD |
B3LYP/ AVTZ |
CAM-B3LYP/ SNSD |
CAM-B3LYP/ AVTZ |
B2PLYP/ AVTZ |
MP2/ AVTZ |
best “cheap”a |
bestCC (TZ,QZ)/(CT)b |
semi-exp rec |
|---|---|---|---|---|---|---|---|---|---|
| Bonds | |||||||||
| O1-C2 | 1.4371 | 1.4344 | 1.4262 | 1.4235 | 1.4372 | 1.4392 | 1.4331 | 1.4289 | 1.4305 |
| O1-C3 | 1.4354 | 1.4326 | 1.4257 | 1.4299 | 1.4366 | 1.4404 | 1.4341 | 1.4299 | 1.4323 |
| C2-C3 | 1.4684 | 1.4644 | 1.4628 | 1.4587 | 1.4627 | 1.4630 | 1.4605 | 1.4600 | 1.4601 |
| C2-C7 | 1.5057 | 1.5017 | 1.5005 | 1.4966 | 1.4997 | 1.4972 | 1.4968 | 1.4969 | 1.4985 |
| C2-H6 | 1.0919 | 1.0872 | 1.0906 | 1.0861 | 1.0854 | 1.0853 | 1.0851 | 1.0852 | 1.0847 |
| C3-H4 | 1.0898 | 1.0853 | 1.0887 | 1.0843 | 1.0834 | 1.0833 | 1.0831 | 1.0837 | 1.0827 |
| C3-H5 | 1.0893 | 1.0849 | 1.0881 | 1.0837 | 1.0828 | 1.0824 | 1.0822 | 1.0826 | 1.0824 |
| C7-H8 | 1.0942 | 1.0849 | 1.0931 | 1.0886 | 1.0884 | 1.0886 | 1.0886 | 1.0881 | 1.0871 |
| C7-H9 | 1.0964 | 1.0918 | 1.0949 | 1.0903 | 1.0904 | 1.0903 | 1.0902 | 1.0900 | 1.0897 |
| C7-H10 | 1.0956 | 1.0912 | 1.0942 | 1.0898 | 1.0896 | 1.0895 | 1.0893 | 1.0890 | 1.0882 |
| MAE-re(SE)d | 0.0068 | 0.0027 | 0.0050 | 0.0028 | 0.0020 | 0.0026 | 0.0011 | 0.0009 | |
| ∣MAX∣-re(SE)d | 0.0084 | 0.0043 | 0.0066 | 0.0093 | 0.0067 | 0.0087 | 0.0026 | 0.0024 | |
| MAE-bestCCe | 0.0070 | 0.0031 | 0.0044 | 0.0018 | 0.0022 | 0.0026 | 0.0011 | ||
| ∣MAX∣bestCCe | 0.0088 | 0.0055 | 0.0055 | 0.0070 | 0.0083 | 0.0105 | 0.0042 |
| Angles | |||||||||
| C2-O1-C3 | 61.49 | 61.43 | 61.72 | 61.66 | 61.19 | 61.07 | 61.12 | 61.44 | 61.33 |
| C3-C2-C7 | 122.54 | 122.63 | 122.28 | 122.33 | 122.27 | 121.66 | 121.88 | 121.73 | 121.68 |
| C3-C2-H6 | 116.99 | 116.98 | 117.09 | 117.09 | 117.06 | 117.10 | 117.15 | 117.22 | 117.31 |
| C2-C3-H4 | 119.26 | 119.28 | 119.14 | 119.14 | 119.09 | 118.71 | 118.88 | 118.84 | 118.96 |
| C2-C3-H5 | 120.10 | 120.14 | 120.10 | 120.15 | 120.12 | 120.02 | 120.14 | 120.07 | 119.89 |
| C2-C7-H8 | 110.75 | 110.80 | 110.53 | 110.56 | 110.52 | 110.07 | 110.24 | 110.17 | 110.29 |
| C2-C7-H9 | 110.75 | 110.43 | 110.53 | 110.51 | 110.43 | 110.48 | 110.39 | 110.48 | 110.43 |
| C2-C7-H10 | 110.61 | 110.59 | 110.59 | 110.56 | 110.53 | 110.48 | 110.39 | 110.54 | 110.31 |
| H4-C3-C2-O1 | 103.24 | 103.33 | 103.29 | 103.39 | 103.18 | 103.09 | 102.88 | 103.21 | 103.04 |
| H5-C3-C2-O1 | −103.03 | −103.09 | −103.02 | −103.08 | −102.88 | −102.66 | −102.53 | −102.84 | −102.66 |
| H6-C2-C3-O1 | 101.92 | 101.97 | 102.01 | 102.09 | 101.90 | 101.93 | 101.79 | 102.04 | 101.91 |
| H8-C7-C2-C3 | 25.02 | 25.15 | 25.19 | 25.25 | 25.02 | 25.12 | 23.89 | 24.84 | 25.35 |
| H9-C7-C2-C3 | −95.44 | −95.31 | −95.25 | −95.18 | −95.39 | −95.23 | −96.46 | −95.47 | −95.20 |
| H10-C7-C2-C3 | 145.12 | 145.29 | 145.14 | 145.24 | 145.05 | 144.94 | 143.84 | 144.73 | 145.04 |
| MAE-re(SE)d | 0.30 | 0.29 | 0.23 | 0.25 | 0.19 | 0.12 | 0.38 | 0.18 | |
| ∣MAX∣-re(SE)d | 0.87 | 0.95 | 0.60 | 0.65 | 0.59 | 0.26 | 1.45 | 0.51 | |
| MAE-bestCCe | 0.24 | 0.28 | 0.21 | 0.24 | 0.17 | 0.15 | 0.34 | ||
| ∣MAX∣bestCCe | 0.82 | 0.90 | 0.55 | 0.60 | 0.54 | 0.37 | 0.99 |
a
Best-estimated equilibrium structure obtained by means of the “cheap” scheme (Eq. (3)).
b
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.
c
Semi-experimental equilibrium structure: this work.
d
Mean absolute error (MAE) and maximum absolute deviations (∣MAX∣) with respect to the semi-experimental equilibrium structure.
e
Mean absolute error (MAE) and maximum absolute deviations (∣MAX∣) with respect to the best-estimated (bestCC) parameters.