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The vibrational frequencies of CH2OH
10 December 1993
Volume 2 15, number 5
The vibrational frequencies of CH20H Charles W. Bauschlicher Jr. and Harry Partridge NASAAmes Research Center, Moffett Field, C4 94035, USA Received 26 July 1993; in final form 24 September 1993
On the basis of the comparison of the experimental and calculated vibrational frequencies of CHsOH and CHsOH, it is concluded that the band observed by Jacox at 569 cm-’ is due to the CHI rock in CHsOH. Calculations, using a second-order MollerPlesset perturbation theory and a coupled-cluster singles and doubles approach including a perturbational estimate of the triple excitations, show that this mode is more sensitive to basis set than the other modes. Agreement with experiment is obtained only when very large basis sets are used.
1. Introduction
In 1981 Jacox [ 1 ] formed CHzOH in solid Ar by the reaction of CH,OH with excited Ar atoms or F atoms. Six of the nine vibrational modes were observed for the CHzOH radicals formed by either reaction. An additional transition was observed at 569 cm-’ when the CHzOH was formed by reaction with F atoms, but not with excited Ar atoms. As discussed by Jacox, this mode could correspond to the CHz rock in CHzOH or correspond to a CHzOHnHF mode. Thus, the assignment of this mode to CHzOH was in some doubt. For example, Jacox [ 2 ] did not discuss the 569 cm-’ band in her 1988 review. In 1983 Saebo, Kadom and Schaefer [3] computed the vibrational frequencies of CHSOH and CHzOH at the self-consistent-field (SCF) level using a 6-3 lG* basis set. After scaling the computed frequencies by 0.9, they found that all of their frequencies agreed reasonably well with experiment except the CH2 rock, which they found at 765 cm-‘, or almost 200 cm- ’ larger than the 569 cm-’ frequency observed in experiment. This would appear to be further support for not assigning this band to CHzOH. However, in 199 1 Glauser and Koszykowski [4] found a much lower frequency (635 cm-’ ) using a 6-3 1G” basis set and secondorder Moller-Plesset perturbation theory [ 5 ] (MP2). Unfortunately this work is flawed by an error; as we show below, the C,, geometry that they re-
ported is a saddle point and their lowest vibrational frequency should have been reported as 527i cm-‘. In this Letter we report on calculations that show the CHz rock in CHzOH is more sensitive to basis set than the other modes of CHzOH or the modes in CHSOH. Our best calculations support the assignment of the band observed by Jacox at 569 cm-’ to CHZOH.
2. Methods
The basis sets employed are those developed by Pople and co-workers [ 61. For CHzOH we use the spin-unrestricted approach. The geometries are optimized at each level of theory for each basis set and the harmonic frequencies computed at that geometry. The SCF and MP2 calculations are performed using GAUSSIAN 90 [ 7 1. The coupled-cluster singles and doubles approach [ 81 including a perturbational estimate of the triple excitations [ 91 (denoted CCSD (T) ) calculations are performed using ACES II I’.
3. Results and discussion
We tirst consider CH30H where accurate experimental fundamentals [ 10 ] are available for comparison. The calculations of Lee and Rice [ 111 show
0009-2614/93/% 06.00 0 1993 Elsevier Science Publishers B.V. All rights reserved.
451
Volume 2 15, number 5
CHEMICAL PHYSICS LETTERS
that the CCSD(T) and MP2 methods yield very similar harmonic frequencies in a double zeta plus polarization basis set; excluding the X-H stretches the largest difference was 20 cm-‘. The MP2 optimized geometry is given in table 1. The results are in good agreement with previous theoretical results at the MP2 level [ 4,111 or CCSD (T) level [ 111 and with the vibrational averaged experimental results
t121. We compute the harmonic frequencies at the MP2 level using the 6-3 11G”* and 6-3 1 1 + G ( 3df, 2p ) basis sets. These results along with the experimental fundamentals are given in table 2. We first note that there are no large changes in the frequencies with basis set improvement. This combined with the small difference between the CCSD(T) and MP2 results, I’ ACES II is computational chemistry package especially designed for coupled-cluster and many-body perturbation calculations. The SCF, transformation, correlation energy and gradient codes were written by J.F. Stanton, J. Gauss, J.D. Watts, W.J. Lauderdale and R.J. Bartlett. The two-electron integrals are taken from the vectorized MOLECULE code of J. Almlof and P.R. Taylor. ACES II includes a modified version of the ABACUS integral derivatives program, written by T. Helgaker, H.J. Jensen, P. Jerensen, J. Olsen and P.R. Taylor, and the geometry optimization and vibrational analysis package written by J.F. Stanton and D.E. Bemholdt.
Table 1 Summary of the geometrical parameters computed at the MP2 level in the 6-311 +G( 3df, 2p) basis set. The bond lengths are in A and the angles in deg. H., is the H atom bonded to the 0 atom, while I-L., for n = a, b, and c are the H atoms bonded to the carbon atom. CHsOH has C, symmetry while CHsOH has C, symmetry
452
Degreeof freedom
CHsOH
c-o O-H,, C-H, C-H.,, C-H, L H,OC LOCH, LOCI% LOCH, HCGCH, I-bGCH& %CJCH,
1.4147 0.9576 1.0896 1.0896 1.0841 108.58 112.05 112.05 106.71 61.52 -61.52 180.0
CHsOH 1.3586 0.9583 1.077 1 1.0734 109.45 118.81 113.54 28.43 175.44
10 December 1993
Table 2 Summary of the computed harmonic frequencies (in cm-‘) for CHsOH. The experimental fundamentals are also given for comparison 6-3110”
WI 01 w3 w4 05
06 w7 Ws 09 010 011 a12 “Ref.
6-311+0(3df,
2p)
SCF
MP2
MP2
scakd
4187 3257 3141 1630 1615 1489 1160 1179 3185 1619 1277 342
3929 3190 3051 1518 1537 1404 1117 1091 3116 1518 1198 347
3907 3201 3071 1542 1505 1378 1103 1073 3141 1532 1198 294
3688 3022 2899 1456 1421 1301 1041 1013 2965 1447 1130 278
Exp. a)
3681 3000 2844 1477 1455 1345 1060 1033 2960 1477 1165 295
Ill].
leads us to conclude that the computed harmonic frequencies should be reasonably accurate. To improve the agreement with experiment, we perform a least-squares fit to determine a single scale factor to obtain the best fit with experiment. These results are reported in table 2 under the column labeled “scaled”. The agreement between these results and experiment is very good and consistent with the expected difference in the anharmonic effects for an X-H stretch compared with the other modes. We treat CHzOH at the same levels as CHSOH. The optimized MP2 geometry using the 63 11 + G( 3df, 2p) basis set is given in table 1. The molecule has Cr symmetry as found at the SCF level, not C,, as reported by Glauser and Koszykowski [ 41. To resolve this difference we optimized the geometry at the MP2 level using the same 6-31G9 basis set; we find that the C1 structure is 4.4 kcal/mol below the C,. For the C, structure, we reproduce their frequencies with the exception that the vibrational frequency that they report at 527 cm-‘, should in fact be 527i cm-‘. The C, structure is more stable as the open-shell orbital on carbon can interact with the oxygen lone pair. We also note that the CH2 rocking frequency at the MP2 level in the 6-31G” basis for the C, structure is 782 cm-‘, which is very different from that value obtained for the C, structure. Thus once the error is corrected, the level of theory used
Volume 2 15, number 5
CHEMICAL PHYSICS LETTERS
10 December 1993
Table 3 Summary of the computed harmonic frequencies (in cm-’ ) for CHsOH. The experimental fundamentals are also given for comparison 6.311+G’“’ MP2
6.311G” SCF
CCSD(T)
MP2
4179 3386 3249 1610 1476 1266 1153 878 399
3894 3264 3123 1511 1399 1215 1075 704 459
3928 3331 3180 1529 1399 1237 1090 726 465
3914 3342 3190 1520 1382 1223 1081 690 444
6.311+G(3df,
2p)
MP2
scaled
3904 3361 3211 1519 1372’ 1232 1074 612 438
3688 3175 3033 1435 1296 1164 1014 578 413
Exp. .’
3650
1459 1334 1183 1048 569 420
‘) Ref. [l].
by Glauser and Koszykowski [4] does not support assigning the 569 cm-’ band to CHIOH. There are sizeable changes in the harmonic frequencies between the SCF and CCSD (T) levels, but none of the changes are unexpectedly large - see table 3. The MP2 frequencies are in good agreement with the CCSD (T) results. In this regard we note that for wg (the CHI rock) the CCSD(T) frequency is only 22 cm-’ smaller than the MP2 value. At the MP2 level, the 6-3 11G” basis set yields a frequency for d&rthat is 56 cm-’ smaller than that obtained using the 6-3 1G*+ basis set. Clearly this mode is sensitive to one-particle basis set size. We then expand the basis set at the MP2 level. Increasing the basis set from 6-3 1lG++ to 6-311+ G+* (i.e. adding diffuse functions) makes only modest difference in the results, with the largest shift coming for 08 which is shifted 36 cm-’ to lower frequency. Expanding the basis set further to include additional polarization functions gives a dramatic decrease in w& relative to the changes observed for CHSOH or the other modes in CHIOH. It is interesting to note that computing the frequencies using the correlation-consistent polarized valence triple-zeta sets of Dunning [ 13 ] at the MP2 level yields essentially the same frequencies as the 6-3 11 + G( 3df, 2p) basis set; the average absolute error is 7 cm-’ for both molecules, the maximum changes are 13 cm- ’ for CHzOH and 17 cm- l for CH,OH, and the wg frequency of CHzOH differs by only 1 cm- I between the two basis sets. As for CH30H, we determine the optimal scale factor for the CHzOH frequencies. (Note that the
optimal scale factor for CHzOH (0.9446) is almost identical to that for CHaOH ( 0.9440 ) . ) At this level, all of the frequencies are in good agreement with experiment [ 11, including @. Thus we conclude that the mode at 569 cm-’ observed by Jacox [ 1 ] is in fact the CHz rock in CHIOH. On the basis of our CH,OH results, our scaled values for the two unobserved C-H stretches in CHzOH are probably about 25 + 25 cm-’ too high. Thus our best estimate for these two frequencies is 3008 and 3 150 cm-‘. These values are very similar with the estimate of 2960 and 3084 cm-’ by Saebo, Radom, and Schaefer [ 3 1. The similarity of the two estimates is important as these frequencies are needed to compute the zero-point energy and the thermodynamic correction both of which are required in the calculation of the CH20H heat of formation at 298 K, which has been of considerable interest recently. Basis set incompleteness in CHIOH leads to an w8 frequency that is too small. Simandiras et al. [ 141 found for C2H2 that improving the basis set dramatically increased the out-of-plane bending frequency. It was later shown [ 15 ] that most of this basis set effect for CzH2 was as a result of decreasing the basis set superposition error. Thus it appears that basis set improvements can dramatically increase or decrease computed bending frequencies.
4. Conclusions The harmonic frequencies of CHzOH and CH30H 453
Volume 2 15, number 5
CHEMICAL PHYSICS LETTERS
have been computed at several levels of theory. All of the modes of CH30H and CH,OH, except the CH2 rock in CH,OH, behave in a similar manner with improvement in the basis set or correlation treatment. Therefore reasonable agreement with the experimental fundamentals can be obtained by scaling any of the computed results. The frequency for the CH2 rock is much more sensitive to the basis set. However, once a large basis set is used, even this mode is in good agreement with experiment. Thus we conclude that the band at 569 cm-’ should be assigned as the us in CH20H.
References [l] ME. Jacox, Chem. Phys. 59 (1981) 213. [2] M.E. Jacox, J. Phys. Chem. Ref. Data 17 (1988) 269. [ 31 S. Saebo, L. Radom and H.F. Schaefer, J. Chem. Phys 78 (1983) 845. [4] W.A. Glauser and M.L. Koszykowski, J. Phys. Chem. 95 (1991) 10705.
454
10 December 1993
[ 5 ] J.A. Pople, J.S. Binkley and R. Seeger, Intern. J. Quantum Chem. Symp. 10 (1976) 1. [6] M.J. Frisch, J.A. Pople and J.S. Binkley, J. Chem. Phys. 80 ( 1984) 3265, and references therein. [7] M.J. Frisch, M. Head-Gordon, G.W. Trucks, J.B. Foresman, H.B. Schlegel, K. Raghavachari, M. Robb, J.S. Binkley, C. Gonzalez, D.J. DeFmes, D.J. Fox, RA. Whiteside, R Seeger, C.F. Melius, J. Baker, R.L. Martin, L.R. Kahn, J.J.P. Stewart, S. Topiol and J.A. Pople, GAUSSIAN (Gaussian, Pittsburgh, 1990). (81 R.J. Bartlett, Ann. Rev. Phys. Chem. 32 (1981) 359. [9] K. Raghavachari, G.W. Trucks, J.A. Pople and M. HeadGordon, Chem. Phys. Letters 157 (1989) 479. [lo] T. Shimanouchi, Tables of molecular vibrational frequencies, NBS (US GPO, Washington, 1972). [11]T.J.LeeandJ.E.Rice,J.Am.Chem.Soc.114(1992)8248. [ 121 M.D. Harmony, V.W. Laurie, R.L. Kuczkowski, R.H. Schwendeman, D.A. Ramsay, F.J. Lovas, W.L. Le.&rty and A.G. Maki, J. Phys. Chem. Ref. Data 8 (1979) 619. [ 131 T.H. Dunning, J. Chem. Phys. 90 (1989) 1007. [ 141 E.D. Simandiras, J.E. Rice, T.J. Lee, R.D. Amos and N.C. Handy, J. Chem. Phys. 88 (1988) 3187. [ 151 P.R. Taylor, private communication.
Volume 2 15, number 5
The vibrational frequencies of CH20H Charles W. Bauschlicher Jr. and Harry Partridge NASAAmes Research Center, Moffett Field, C4 94035, USA Received 26 July 1993; in final form 24 September 1993
On the basis of the comparison of the experimental and calculated vibrational frequencies of CHsOH and CHsOH, it is concluded that the band observed by Jacox at 569 cm-’ is due to the CHI rock in CHsOH. Calculations, using a second-order MollerPlesset perturbation theory and a coupled-cluster singles and doubles approach including a perturbational estimate of the triple excitations, show that this mode is more sensitive to basis set than the other modes. Agreement with experiment is obtained only when very large basis sets are used.
1. Introduction
In 1981 Jacox [ 1 ] formed CHzOH in solid Ar by the reaction of CH,OH with excited Ar atoms or F atoms. Six of the nine vibrational modes were observed for the CHzOH radicals formed by either reaction. An additional transition was observed at 569 cm-’ when the CHzOH was formed by reaction with F atoms, but not with excited Ar atoms. As discussed by Jacox, this mode could correspond to the CHz rock in CHzOH or correspond to a CHzOHnHF mode. Thus, the assignment of this mode to CHzOH was in some doubt. For example, Jacox [ 2 ] did not discuss the 569 cm-’ band in her 1988 review. In 1983 Saebo, Kadom and Schaefer [3] computed the vibrational frequencies of CHSOH and CHzOH at the self-consistent-field (SCF) level using a 6-3 lG* basis set. After scaling the computed frequencies by 0.9, they found that all of their frequencies agreed reasonably well with experiment except the CH2 rock, which they found at 765 cm-‘, or almost 200 cm- ’ larger than the 569 cm-’ frequency observed in experiment. This would appear to be further support for not assigning this band to CHzOH. However, in 199 1 Glauser and Koszykowski [4] found a much lower frequency (635 cm-’ ) using a 6-3 1G” basis set and secondorder Moller-Plesset perturbation theory [ 5 ] (MP2). Unfortunately this work is flawed by an error; as we show below, the C,, geometry that they re-
ported is a saddle point and their lowest vibrational frequency should have been reported as 527i cm-‘. In this Letter we report on calculations that show the CHz rock in CHzOH is more sensitive to basis set than the other modes of CHzOH or the modes in CHSOH. Our best calculations support the assignment of the band observed by Jacox at 569 cm-’ to CHZOH.
2. Methods
The basis sets employed are those developed by Pople and co-workers [ 61. For CHzOH we use the spin-unrestricted approach. The geometries are optimized at each level of theory for each basis set and the harmonic frequencies computed at that geometry. The SCF and MP2 calculations are performed using GAUSSIAN 90 [ 7 1. The coupled-cluster singles and doubles approach [ 81 including a perturbational estimate of the triple excitations [ 91 (denoted CCSD (T) ) calculations are performed using ACES II I’.
3. Results and discussion
We tirst consider CH30H where accurate experimental fundamentals [ 10 ] are available for comparison. The calculations of Lee and Rice [ 111 show
0009-2614/93/% 06.00 0 1993 Elsevier Science Publishers B.V. All rights reserved.
451
Volume 2 15, number 5
CHEMICAL PHYSICS LETTERS
that the CCSD(T) and MP2 methods yield very similar harmonic frequencies in a double zeta plus polarization basis set; excluding the X-H stretches the largest difference was 20 cm-‘. The MP2 optimized geometry is given in table 1. The results are in good agreement with previous theoretical results at the MP2 level [ 4,111 or CCSD (T) level [ 111 and with the vibrational averaged experimental results
t121. We compute the harmonic frequencies at the MP2 level using the 6-3 11G”* and 6-3 1 1 + G ( 3df, 2p ) basis sets. These results along with the experimental fundamentals are given in table 2. We first note that there are no large changes in the frequencies with basis set improvement. This combined with the small difference between the CCSD(T) and MP2 results, I’ ACES II is computational chemistry package especially designed for coupled-cluster and many-body perturbation calculations. The SCF, transformation, correlation energy and gradient codes were written by J.F. Stanton, J. Gauss, J.D. Watts, W.J. Lauderdale and R.J. Bartlett. The two-electron integrals are taken from the vectorized MOLECULE code of J. Almlof and P.R. Taylor. ACES II includes a modified version of the ABACUS integral derivatives program, written by T. Helgaker, H.J. Jensen, P. Jerensen, J. Olsen and P.R. Taylor, and the geometry optimization and vibrational analysis package written by J.F. Stanton and D.E. Bemholdt.
Table 1 Summary of the geometrical parameters computed at the MP2 level in the 6-311 +G( 3df, 2p) basis set. The bond lengths are in A and the angles in deg. H., is the H atom bonded to the 0 atom, while I-L., for n = a, b, and c are the H atoms bonded to the carbon atom. CHsOH has C, symmetry while CHsOH has C, symmetry
452
Degreeof freedom
CHsOH
c-o O-H,, C-H, C-H.,, C-H, L H,OC LOCH, LOCI% LOCH, HCGCH, I-bGCH& %CJCH,
1.4147 0.9576 1.0896 1.0896 1.0841 108.58 112.05 112.05 106.71 61.52 -61.52 180.0
CHsOH 1.3586 0.9583 1.077 1 1.0734 109.45 118.81 113.54 28.43 175.44
10 December 1993
Table 2 Summary of the computed harmonic frequencies (in cm-‘) for CHsOH. The experimental fundamentals are also given for comparison 6-3110”
WI 01 w3 w4 05
06 w7 Ws 09 010 011 a12 “Ref.
6-311+0(3df,
2p)
SCF
MP2
MP2
scakd
4187 3257 3141 1630 1615 1489 1160 1179 3185 1619 1277 342
3929 3190 3051 1518 1537 1404 1117 1091 3116 1518 1198 347
3907 3201 3071 1542 1505 1378 1103 1073 3141 1532 1198 294
3688 3022 2899 1456 1421 1301 1041 1013 2965 1447 1130 278
Exp. a)
3681 3000 2844 1477 1455 1345 1060 1033 2960 1477 1165 295
Ill].
leads us to conclude that the computed harmonic frequencies should be reasonably accurate. To improve the agreement with experiment, we perform a least-squares fit to determine a single scale factor to obtain the best fit with experiment. These results are reported in table 2 under the column labeled “scaled”. The agreement between these results and experiment is very good and consistent with the expected difference in the anharmonic effects for an X-H stretch compared with the other modes. We treat CHzOH at the same levels as CHSOH. The optimized MP2 geometry using the 63 11 + G( 3df, 2p) basis set is given in table 1. The molecule has Cr symmetry as found at the SCF level, not C,, as reported by Glauser and Koszykowski [ 41. To resolve this difference we optimized the geometry at the MP2 level using the same 6-31G9 basis set; we find that the C1 structure is 4.4 kcal/mol below the C,. For the C, structure, we reproduce their frequencies with the exception that the vibrational frequency that they report at 527 cm-‘, should in fact be 527i cm-‘. The C, structure is more stable as the open-shell orbital on carbon can interact with the oxygen lone pair. We also note that the CH2 rocking frequency at the MP2 level in the 6-31G” basis for the C, structure is 782 cm-‘, which is very different from that value obtained for the C, structure. Thus once the error is corrected, the level of theory used
Volume 2 15, number 5
CHEMICAL PHYSICS LETTERS
10 December 1993
Table 3 Summary of the computed harmonic frequencies (in cm-’ ) for CHsOH. The experimental fundamentals are also given for comparison 6.311+G’“’ MP2
6.311G” SCF
CCSD(T)
MP2
4179 3386 3249 1610 1476 1266 1153 878 399
3894 3264 3123 1511 1399 1215 1075 704 459
3928 3331 3180 1529 1399 1237 1090 726 465
3914 3342 3190 1520 1382 1223 1081 690 444
6.311+G(3df,
2p)
MP2
scaled
3904 3361 3211 1519 1372’ 1232 1074 612 438
3688 3175 3033 1435 1296 1164 1014 578 413
Exp. .’
3650
1459 1334 1183 1048 569 420
‘) Ref. [l].
by Glauser and Koszykowski [4] does not support assigning the 569 cm-’ band to CHIOH. There are sizeable changes in the harmonic frequencies between the SCF and CCSD (T) levels, but none of the changes are unexpectedly large - see table 3. The MP2 frequencies are in good agreement with the CCSD (T) results. In this regard we note that for wg (the CHI rock) the CCSD(T) frequency is only 22 cm-’ smaller than the MP2 value. At the MP2 level, the 6-3 11G” basis set yields a frequency for d&rthat is 56 cm-’ smaller than that obtained using the 6-3 1G*+ basis set. Clearly this mode is sensitive to one-particle basis set size. We then expand the basis set at the MP2 level. Increasing the basis set from 6-3 1lG++ to 6-311+ G+* (i.e. adding diffuse functions) makes only modest difference in the results, with the largest shift coming for 08 which is shifted 36 cm-’ to lower frequency. Expanding the basis set further to include additional polarization functions gives a dramatic decrease in w& relative to the changes observed for CHSOH or the other modes in CHIOH. It is interesting to note that computing the frequencies using the correlation-consistent polarized valence triple-zeta sets of Dunning [ 13 ] at the MP2 level yields essentially the same frequencies as the 6-3 11 + G( 3df, 2p) basis set; the average absolute error is 7 cm-’ for both molecules, the maximum changes are 13 cm- ’ for CHzOH and 17 cm- l for CH,OH, and the wg frequency of CHzOH differs by only 1 cm- I between the two basis sets. As for CH30H, we determine the optimal scale factor for the CHzOH frequencies. (Note that the
optimal scale factor for CHzOH (0.9446) is almost identical to that for CHaOH ( 0.9440 ) . ) At this level, all of the frequencies are in good agreement with experiment [ 11, including @. Thus we conclude that the mode at 569 cm-’ observed by Jacox [ 1 ] is in fact the CHz rock in CHIOH. On the basis of our CH,OH results, our scaled values for the two unobserved C-H stretches in CHzOH are probably about 25 + 25 cm-’ too high. Thus our best estimate for these two frequencies is 3008 and 3 150 cm-‘. These values are very similar with the estimate of 2960 and 3084 cm-’ by Saebo, Radom, and Schaefer [ 3 1. The similarity of the two estimates is important as these frequencies are needed to compute the zero-point energy and the thermodynamic correction both of which are required in the calculation of the CH20H heat of formation at 298 K, which has been of considerable interest recently. Basis set incompleteness in CHIOH leads to an w8 frequency that is too small. Simandiras et al. [ 141 found for C2H2 that improving the basis set dramatically increased the out-of-plane bending frequency. It was later shown [ 15 ] that most of this basis set effect for CzH2 was as a result of decreasing the basis set superposition error. Thus it appears that basis set improvements can dramatically increase or decrease computed bending frequencies.
4. Conclusions The harmonic frequencies of CHzOH and CH30H 453
Volume 2 15, number 5
CHEMICAL PHYSICS LETTERS
have been computed at several levels of theory. All of the modes of CH30H and CH,OH, except the CH2 rock in CH,OH, behave in a similar manner with improvement in the basis set or correlation treatment. Therefore reasonable agreement with the experimental fundamentals can be obtained by scaling any of the computed results. The frequency for the CH2 rock is much more sensitive to the basis set. However, once a large basis set is used, even this mode is in good agreement with experiment. Thus we conclude that the band at 569 cm-’ should be assigned as the us in CH20H.
References [l] ME. Jacox, Chem. Phys. 59 (1981) 213. [2] M.E. Jacox, J. Phys. Chem. Ref. Data 17 (1988) 269. [ 31 S. Saebo, L. Radom and H.F. Schaefer, J. Chem. Phys 78 (1983) 845. [4] W.A. Glauser and M.L. Koszykowski, J. Phys. Chem. 95 (1991) 10705.
454
10 December 1993
[ 5 ] J.A. Pople, J.S. Binkley and R. Seeger, Intern. J. Quantum Chem. Symp. 10 (1976) 1. [6] M.J. Frisch, J.A. Pople and J.S. Binkley, J. Chem. Phys. 80 ( 1984) 3265, and references therein. [7] M.J. Frisch, M. Head-Gordon, G.W. Trucks, J.B. Foresman, H.B. Schlegel, K. Raghavachari, M. Robb, J.S. Binkley, C. Gonzalez, D.J. DeFmes, D.J. Fox, RA. Whiteside, R Seeger, C.F. Melius, J. Baker, R.L. Martin, L.R. Kahn, J.J.P. Stewart, S. Topiol and J.A. Pople, GAUSSIAN (Gaussian, Pittsburgh, 1990). (81 R.J. Bartlett, Ann. Rev. Phys. Chem. 32 (1981) 359. [9] K. Raghavachari, G.W. Trucks, J.A. Pople and M. HeadGordon, Chem. Phys. Letters 157 (1989) 479. [lo] T. Shimanouchi, Tables of molecular vibrational frequencies, NBS (US GPO, Washington, 1972). [11]T.J.LeeandJ.E.Rice,J.Am.Chem.Soc.114(1992)8248. [ 121 M.D. Harmony, V.W. Laurie, R.L. Kuczkowski, R.H. Schwendeman, D.A. Ramsay, F.J. Lovas, W.L. Le.&rty and A.G. Maki, J. Phys. Chem. Ref. Data 8 (1979) 619. [ 131 T.H. Dunning, J. Chem. Phys. 90 (1989) 1007. [ 141 E.D. Simandiras, J.E. Rice, T.J. Lee, R.D. Amos and N.C. Handy, J. Chem. Phys. 88 (1988) 3187. [ 151 P.R. Taylor, private communication.