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Comment on “A computational study of the structures of van der Waals and hydrogen-bonded complexes of ethene and ethyne”
6 December 1996
CHEMICAL PHYSICS LETTERS
ELSEVIER
Chemical Physics Letters 263 (1996) 345-347
Comment
Comment on "A computational study of the structures of van der Waals and hydrogen-bonded complexes of ethene and ethyne" Ho
Young Jeong a, Young-Kyu Han b
a Kumho Chemical Laboratories, P.O. Box 64. Yuseong, Taejon 305-600, South Korea b Department of Chemistry. Korea Advanced Institute of Science and Technology, Taejon 305-701, South Korea
Received 15 July 1996; in final form 13 September 1996
Abstract
The weakly bonded complexes C2H2-C12 and C2Hz-HC1 are studied using extended basis sets at the HE BLYR B3LYP, and MP2 levels of theory. The interaction energies obtained from BLYP and B3LYP for the C2H2-C12 and the C2H2-HCI are smaller than those from MP2 in our calculations. It is necessary that the extended basis set should be used in order to compare between the binding energies from various levels of theory for the investigation of weakly bonded complexes.
A recent paper [ 1 ] by Kang was concerned with the structures of van der Waals (X-CI2) and hydrogenbonded complexes (X-HC1) of ethene and ethyne (X = C2H4 or C2H2). The author studied the structures using various level of theory such as density functional, hybrid density functional, Hartree-Fock and MP2 calculations, and reported structures, binding energies, distortion constants and softest normal mode frequencies of these complexes. We will particularly concentrate on the binding energies among his results in this Comment. Kang regarded the MP2 calculation as a standard in comparison from the binding energies obtained from the other methods. The gist of Kang's results is as follows: 1. Both the BLYP and B3LYP functionals overestimate the binding energy of the van der Waals complexes by a significant margin. 2. For the hydrogen-bonded complexes, the pure density functional method BLYP show better agreement with the MP2 results than any hybrid density functional methods. 3. The density functional methods BLYP, B3P, and
B3LYP provide more accurate binding energies for the hydrogen-bonded complexes X-HC! than for the van der Waals complexes X-CI2 Kang calculated all structures using only the 631 l G(d) basis set. We doubted if this basis set is sufficient for qualitative comparisons of DFT with MP2 methods in the weakly bound complexes, and for describing X-HCI and X-C12 (X = C2H4 or C2H2) systems with equal quality. Thus we performed the calculations for C2H2-C12 and C2H2-HCi using basis sets with multiple polarization functions and diffuse functions at the HF, BLYP, B3LYP, and MP2 levels of theory. These complexes are T-shaped in which the C12 or HCI molecular axis is perpendicular to the C2H2 molecule and points at the midpoint of its 77"bond. The optimized bond lengths and binding energies from the calculations are listed in Table 1. The effect of basis set superposition error(BSSE) was corrected using the counterpoise method [2] by single point calculations. The results in Table 1 using the 6-31 1G(d) basis set confirm Kang's calculation. However, the results using the 6-311++G(3df,2pd) basis set, the
0009-2614/96/$12.00 Copyright (~) 1996 Published by Elsevier Science B.V. All rights reserved. PHS0009-2614(96)01214-6
346
H.Y Jeong. Y-K. Han/Chemical Physics Letters 263 (1996) 345-347
Table 1 Optimized bond lengths (A) and bond energies (kcal/mol) with BSSE correction at the HE BLYE B3LYP, and MP2 levels of theory for C2H2-C12 and C2H2-HCI MP2(HF) 6-31 lg(d)
6-31 lg(2d,p)
6-31 lg(3d,2p)
6-311 ++g(3d,2p)
6-311 ++g(3df,2pd)
C2H2-C12 bond length BSSE (kcal/mol) bond energy
3.14(3.59) 0.92(0.21) 1.27(0.56)
2.98(3.57) 0.98(0.22) 2.09(0.69)
2.90(3.40) 2.33(0.59) 2.11(0.51)
2.94(3.55) 1.84(0.35) 2.05(0.49)
2.99(3.61) 1.41(0.30) 2.11(0.44)
C2H2-HCI bond length BSSE (kcal/mol) bond energy
2.46(2.70) 0.75(0.27) 2.17(I.64)
2.36(2.69) 0.61(0.23) 2.66(1.64)
2.31(2.69) 0.87(0.34) 2.78(1.49)
2.31(2.70) 0.86(0.23) 2.63(1.36)
2.30(2.71) 0.77(0.25) 2.76(1.33)
6-31 lg(d)
6-31 lg(2d,p)
6-31 lg(3d,2p)
6-31 l++g(3d,2p)
6-31 l++g(3df,2pd)
C2H2-CI2 bond length BSSE (kcal/mol) bond energy
2.96(2.83) 0.34(0.39) 2.13(3.26)
2.94(2.82) 0.43(0.54) 1.99(2.77)
2.89(2.79) 1.21(1.36) 1.72(2.45)
2.96(2.84) 0.74(0.81) 1.43(1.97)
2.93(2.91) 0.57(0.62) 1.18(1.54)
C2H2-HCI bond length BSSE (kcal/mol) bond energy
2.39(2.38) 0.38(0.44) 2.52(2.35)
2.37(2.37) 0.37(0.43) 2.39(2.18)
2.38(2.39) 0.44(0.50) 2.21(1.97)
2.39(2.40) 0.31(0.30) 1.99(1.72)
2.40(2.42) 0.32(0.32) 1.94(1.66)
B3LYP(BLYP)
most extended basis set in this Comment, show that the binding energies from BLYP and B3LYP are distinctly smaller than those of MP2. We can see that (B3LYP, C2H2-C12) has about sixty percent of the binding energy calculated by MP2. The basis set extension from 6-311G(d) to 6-31 l + + G ( 3 d f , 2pd) decreases the BLYP and B3LYP binding energies by a significant margin whereas it somewhat increases the MP2 binding energy. Two facts are ascertained from the results employing the various basis sets. First, the binding energies from the 6-311G (2d,p) calculations are converged for both C2H2-C12 and C2H2-HCI in the MP2 scheme, but those from B3LYP and BLYP continuously decrease upon enlargement of the basis set. Second, the 6-311++G(3d,2p) basis set for the C2H2-C12 complex and the 6-311G(2d,p) basis set for C2H2-HC1 are at least necessary for setting correctly the qualitative order of the binding energies in the BLYP, B3LYP, and MP2 methods. According to this, we can judge that Kang's calculations using the
6-311G(d) basis set do not seem to provide even the correct order of the binding energies from DFT and MP2, and to describe the C2H2-C12 and the C2H2HCI with equal quality. In conclusion, the interaction energies obtained from BLYP and B3LYP for both C2H2-C12 and C2H2HC1 are smaller than the binding energies from MP2, in opposition to Kang's results. The lower binding energies from BLYP and B3LYP seem mainly to relate to the failure to properly describe the dispersion force in the DFT scheme [3,4]. The BLYP gives better agreement with the MP2 results than B3LYP for the van der Waals complex C2H2-C12 contrary to Kang's results. Judging from our calculations, it is not clear if the BLYP or B3LYP functional is more accurate for each complex. It is necessary that very extended basis sets including multiple polarization and diffuse functions should be used in order to compare the binding energies from the various levels of theory for the investigation of weakly bonded complexes.
H.Y Jeong, Y-K. Han/Chemical Physics Letters 263 (1996) 345-347
References [I] H.C. Kang, Chem. Phys. Left. 254 (1996) 135. 12] S.E Boys and E Bemardi, Mol. Phys. 19 (1970) 553.
347
[3] B.I. Lundqvist, Y. Andersson, H. Shao, S. Chan and D.C. Langreth, Int. J. Quantum Chem. 56 (1995) 247. I41 S. Kristyan and P. Pulay, Chem. Phys. Lett. 229 (1994) 175.
CHEMICAL PHYSICS LETTERS
ELSEVIER
Chemical Physics Letters 263 (1996) 345-347
Comment
Comment on "A computational study of the structures of van der Waals and hydrogen-bonded complexes of ethene and ethyne" Ho
Young Jeong a, Young-Kyu Han b
a Kumho Chemical Laboratories, P.O. Box 64. Yuseong, Taejon 305-600, South Korea b Department of Chemistry. Korea Advanced Institute of Science and Technology, Taejon 305-701, South Korea
Received 15 July 1996; in final form 13 September 1996
Abstract
The weakly bonded complexes C2H2-C12 and C2Hz-HC1 are studied using extended basis sets at the HE BLYR B3LYP, and MP2 levels of theory. The interaction energies obtained from BLYP and B3LYP for the C2H2-C12 and the C2H2-HCI are smaller than those from MP2 in our calculations. It is necessary that the extended basis set should be used in order to compare between the binding energies from various levels of theory for the investigation of weakly bonded complexes.
A recent paper [ 1 ] by Kang was concerned with the structures of van der Waals (X-CI2) and hydrogenbonded complexes (X-HC1) of ethene and ethyne (X = C2H4 or C2H2). The author studied the structures using various level of theory such as density functional, hybrid density functional, Hartree-Fock and MP2 calculations, and reported structures, binding energies, distortion constants and softest normal mode frequencies of these complexes. We will particularly concentrate on the binding energies among his results in this Comment. Kang regarded the MP2 calculation as a standard in comparison from the binding energies obtained from the other methods. The gist of Kang's results is as follows: 1. Both the BLYP and B3LYP functionals overestimate the binding energy of the van der Waals complexes by a significant margin. 2. For the hydrogen-bonded complexes, the pure density functional method BLYP show better agreement with the MP2 results than any hybrid density functional methods. 3. The density functional methods BLYP, B3P, and
B3LYP provide more accurate binding energies for the hydrogen-bonded complexes X-HC! than for the van der Waals complexes X-CI2 Kang calculated all structures using only the 631 l G(d) basis set. We doubted if this basis set is sufficient for qualitative comparisons of DFT with MP2 methods in the weakly bound complexes, and for describing X-HCI and X-C12 (X = C2H4 or C2H2) systems with equal quality. Thus we performed the calculations for C2H2-C12 and C2H2-HCi using basis sets with multiple polarization functions and diffuse functions at the HF, BLYP, B3LYP, and MP2 levels of theory. These complexes are T-shaped in which the C12 or HCI molecular axis is perpendicular to the C2H2 molecule and points at the midpoint of its 77"bond. The optimized bond lengths and binding energies from the calculations are listed in Table 1. The effect of basis set superposition error(BSSE) was corrected using the counterpoise method [2] by single point calculations. The results in Table 1 using the 6-31 1G(d) basis set confirm Kang's calculation. However, the results using the 6-311++G(3df,2pd) basis set, the
0009-2614/96/$12.00 Copyright (~) 1996 Published by Elsevier Science B.V. All rights reserved. PHS0009-2614(96)01214-6
346
H.Y Jeong. Y-K. Han/Chemical Physics Letters 263 (1996) 345-347
Table 1 Optimized bond lengths (A) and bond energies (kcal/mol) with BSSE correction at the HE BLYE B3LYP, and MP2 levels of theory for C2H2-C12 and C2H2-HCI MP2(HF) 6-31 lg(d)
6-31 lg(2d,p)
6-31 lg(3d,2p)
6-311 ++g(3d,2p)
6-311 ++g(3df,2pd)
C2H2-C12 bond length BSSE (kcal/mol) bond energy
3.14(3.59) 0.92(0.21) 1.27(0.56)
2.98(3.57) 0.98(0.22) 2.09(0.69)
2.90(3.40) 2.33(0.59) 2.11(0.51)
2.94(3.55) 1.84(0.35) 2.05(0.49)
2.99(3.61) 1.41(0.30) 2.11(0.44)
C2H2-HCI bond length BSSE (kcal/mol) bond energy
2.46(2.70) 0.75(0.27) 2.17(I.64)
2.36(2.69) 0.61(0.23) 2.66(1.64)
2.31(2.69) 0.87(0.34) 2.78(1.49)
2.31(2.70) 0.86(0.23) 2.63(1.36)
2.30(2.71) 0.77(0.25) 2.76(1.33)
6-31 lg(d)
6-31 lg(2d,p)
6-31 lg(3d,2p)
6-31 l++g(3d,2p)
6-31 l++g(3df,2pd)
C2H2-CI2 bond length BSSE (kcal/mol) bond energy
2.96(2.83) 0.34(0.39) 2.13(3.26)
2.94(2.82) 0.43(0.54) 1.99(2.77)
2.89(2.79) 1.21(1.36) 1.72(2.45)
2.96(2.84) 0.74(0.81) 1.43(1.97)
2.93(2.91) 0.57(0.62) 1.18(1.54)
C2H2-HCI bond length BSSE (kcal/mol) bond energy
2.39(2.38) 0.38(0.44) 2.52(2.35)
2.37(2.37) 0.37(0.43) 2.39(2.18)
2.38(2.39) 0.44(0.50) 2.21(1.97)
2.39(2.40) 0.31(0.30) 1.99(1.72)
2.40(2.42) 0.32(0.32) 1.94(1.66)
B3LYP(BLYP)
most extended basis set in this Comment, show that the binding energies from BLYP and B3LYP are distinctly smaller than those of MP2. We can see that (B3LYP, C2H2-C12) has about sixty percent of the binding energy calculated by MP2. The basis set extension from 6-311G(d) to 6-31 l + + G ( 3 d f , 2pd) decreases the BLYP and B3LYP binding energies by a significant margin whereas it somewhat increases the MP2 binding energy. Two facts are ascertained from the results employing the various basis sets. First, the binding energies from the 6-311G (2d,p) calculations are converged for both C2H2-C12 and C2H2-HCI in the MP2 scheme, but those from B3LYP and BLYP continuously decrease upon enlargement of the basis set. Second, the 6-311++G(3d,2p) basis set for the C2H2-C12 complex and the 6-311G(2d,p) basis set for C2H2-HC1 are at least necessary for setting correctly the qualitative order of the binding energies in the BLYP, B3LYP, and MP2 methods. According to this, we can judge that Kang's calculations using the
6-311G(d) basis set do not seem to provide even the correct order of the binding energies from DFT and MP2, and to describe the C2H2-C12 and the C2H2HCI with equal quality. In conclusion, the interaction energies obtained from BLYP and B3LYP for both C2H2-C12 and C2H2HC1 are smaller than the binding energies from MP2, in opposition to Kang's results. The lower binding energies from BLYP and B3LYP seem mainly to relate to the failure to properly describe the dispersion force in the DFT scheme [3,4]. The BLYP gives better agreement with the MP2 results than B3LYP for the van der Waals complex C2H2-C12 contrary to Kang's results. Judging from our calculations, it is not clear if the BLYP or B3LYP functional is more accurate for each complex. It is necessary that very extended basis sets including multiple polarization and diffuse functions should be used in order to compare the binding energies from the various levels of theory for the investigation of weakly bonded complexes.
H.Y Jeong, Y-K. Han/Chemical Physics Letters 263 (1996) 345-347
References [I] H.C. Kang, Chem. Phys. Left. 254 (1996) 135. 12] S.E Boys and E Bemardi, Mol. Phys. 19 (1970) 553.
347
[3] B.I. Lundqvist, Y. Andersson, H. Shao, S. Chan and D.C. Langreth, Int. J. Quantum Chem. 56 (1995) 247. I41 S. Kristyan and P. Pulay, Chem. Phys. Lett. 229 (1994) 175.