Quantum Monte Carlo study of the classical barrier height for the H + H2 exchange reaction: Restricted versus unrestricted trial functions
1984; Wiley; Volume: 26; Issue: S18 Linguagem: Inglês
10.1002/qua.560260863
ISSN1097-461X
AutoresPeter J. Reynolds, R. N. Barnett, Will Lester,
Tópico(s)Spectroscopy and Quantum Chemical Studies
ResumoInternational Journal of Quantum ChemistryVolume 26, Issue S18 p. 709-717 Article Quantum Monte Carlo study of the classical barrier height for the H + H2 exchange reaction: Restricted versus unrestricted trial functions P. J. Reynolds, P. J. Reynolds Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720Search for more papers by this authorR. N. Barnett, R. N. Barnett Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 Also at Department of Chemistry, University of California, Berkeley, CA.Search for more papers by this authorW. A. Lester Jr., W. A. Lester Jr. Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 Also at Department of Chemistry, University of California, Berkeley, CA.Search for more papers by this author P. J. Reynolds, P. J. Reynolds Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720Search for more papers by this authorR. N. Barnett, R. N. Barnett Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 Also at Department of Chemistry, University of California, Berkeley, CA.Search for more papers by this authorW. A. Lester Jr., W. A. Lester Jr. Materials and Molecular Research Division, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 Also at Department of Chemistry, University of California, Berkeley, CA.Search for more papers by this author First published: 1/15 March 1984 https://doi.org/10.1002/qua.560260863Citations: 14 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract The fixed-node quantum Monte Carlo (QMC) method is used to obtain the classical barrier height for the H + H2 exchange reaction. Using a spin-restricted, single-determinant trial function ΨT, the authors find that the reaction barrier Eb is less than 9.69 ± 0.25 kcal/mol. This mean value is below the calculated energy barrier obtained by Liu in the most extensive CI calculations on this system. Furthermore, the QMC saddle-point energy of – 1.65903 ± 0.00040 hartrees at the CI-determined geometry lies 0.00027 a.u. (0.17 kcal/mol) below Liu's best CI value. Finally, spinrestricted and spin-unrestricted single-determinant trial functions are contrasted. Although the variational energy 〈ΨT|H|ΨT〉 for an SCF ΨT must be lower for the unrestricted case, this is not true generally for QMC. In fact, we show that if the unrestricted SCF ΨT has the lower QMC energy, then there exists another spin-restricted, single-determinant ΨT whose QMC energy is lower than the QMC energy of the spin-restricted SCF ΨT. Bibliography 1(a) See, for example, A. Kuppermann and G. C. Schatz, J. Chem. Phys. 62, 2502 (1975); 10.1063/1.430733 CASWeb of Science®Google Scholar G. C. Schatz and A. Kuppermann, J. Chem. Phys. 65, 4668 (1976). 10.1063/1.432919 CASWeb of Science®Google Scholar(b) D. G. Truhlar and R. E. Wyatt, in Advances in Chemical Physics, I. Prigogine and S. A. Rice, Eds., (Wiley, New York, 1977), Vol. 36. Google Scholar(c) D. G. Truhlar and R. E. Wyatt, Ann. Rev. Phys. Chem. 27, 1 (1976). 10.1146/annurev.pc.27.100176.000245 CASWeb of Science®Google Scholar 2 J. O. Hirschfelder, H. Eyring, and N. Rosen, J. Chem. Phys. 4, 121 (1936); 10.1063/1.1749798 CASWeb of Science®Google Scholar H. Conroy and B. Bruner, J. Chem. Phys. 42, 4047 (1965); 10.1063/1.1695879 CASWeb of Science®Google Scholar J. Chem. Phys. 47, 921 (1967); 10.1063/1.1712057 CASWeb of Science®Google Scholar I. Shavitt, R. M. Stevens, F. L. Minn, and M. Karplus, J. Chem. Phys. 48, 2700 (1968); 10.1063/1.1669504 CASWeb of Science®Google Scholar C. Edmiston and M. Krauss, J. Chem. Phys. 49, 192 (1968). 10.1063/1.1669809 CASWeb of Science®Google Scholar 3 B. Liu, J. Chem. Phys. 58, 1925 (1973); 10.1063/1.1679454 CASWeb of Science®Google Scholar P. Siegbahn and B. Liu, J. Chem. Phys. 68, 2457 (1978). 10.1063/1.436018 CASWeb of Science®Google Scholar 4 B. Liu, J. Chem. Phys. 80, 581 (1984). 10.1063/1.446441 CASWeb of Science®Google Scholar 5 E. E. Marinero, C. T. Rettner, and R. N. Zare, J. Chem. Phys. 80, 4142 (1984); 10.1063/1.447242 CASWeb of Science®Google Scholar D. P. Gerrity and J. J. Valentini, J. Chem. Phys. 79, 5202 (1983). 10.1063/1.445648 CASWeb of Science®Google Scholar 6(a) J. B. Anderson, J. Chem. Phys. 63, 1499 (1975); 10.1063/1.431514 CASWeb of Science®Google Scholar J. Chem. Phys. 65, 4121 (1976); 10.1063/1.432868 CASWeb of Science®Google Scholar J. Chem. Phys. 73, 3897 (1980). 10.1063/1.440575 CASWeb of Science®Google Scholar(b) P. J. Reynolds, D. M. Ceperley, B. J. Alder, and W. A. Lester, Jr., J. Chem. Phys. 77, 5593 (1982). 10.1063/1.443766 CASWeb of Science®Google Scholar 7 W. L. McMillan, Phys. Rev. 138A, 442 (1965); 10.1103/PhysRev.138.A442 Web of Science®Google Scholar D. M. Ceperley, G. V. Chester, and M. H. Kalos, Phys. Rev. B 16, 3081 (1977). 10.1103/PhysRevB.16.3081 CASWeb of Science®Google Scholar 8(a) M. H. Kalos, Phys. Rev. 128, 1791 (1962); 10.1103/PhysRev.128.1791 Web of Science®Google Scholar J. Comput. Phys. 1, 257 (1967); 10.1016/0021-9991(66)90006-4 Google Scholar(b) M. H. Kalos, D. Levesque, and L. Verlet, Phys. Rev. A 9, 2178 (1974); 10.1103/PhysRevA.9.2178 CASWeb of Science®Google Scholar(c) D. M. Ceperley and M. H. Kalos, in Monte Carlo Methods in Statistical Physics, K. Binder, Ed. (Springer, Berlin, 1979), pp. 145–197; 10.1007/978-3-642-96483-1_4 Google Scholar(d) D. M. Ceperley, in Recent Progress in Many-Body Theories, J. G. Zabolitzky, M. de Llano, M. Fortes, and J. W. Clark, Eds. (Springer, Berlin, 1981), pp. 262–269; 10.1007/BFb0018166 Google Scholar(e) D. M. Ceperley, J. Comput. Phys. 51, 404 (1983). 10.1016/0021-9991(83)90161-4 Web of Science®Google Scholar 9(a) J. W. Moskowitz, K. E. Schmidt, M. A. Lee, and M. H. Kalos, J. Chem. Phys. 77, 349 (1982); 10.1063/1.443612 CASWeb of Science®Google Scholar(b) P. J. Reynolds, M. Dupuis, and W. A. Lester, Jr., "Quantum Monte Carlo Calculation of the Singlet-Triplet Splitting in Methylene" J. Chem. Phys., to appear; Google Scholar(c) R. N. Barnett, P. J. Reynolds, and W. A. Lester, Jr., "The Hydrogen Exchange Reaction: A Quantum Monte Carlo Study" J. Chem. Phys., submitted. Google Scholar 10 N. Metropolis and S. Ulam, J. Am. Stat. Assoc. 44, 335 (1949). 10.1080/01621459.1949.10483310 CASPubMedWeb of Science®Google Scholar 11 D. M. Ceperley, private communication; Google Scholar B. Wells, P. J. Reynolds, and W. A. Lester, Jr., unpublished. Google Scholar 12 R. Jastrow, Phys. Rev. 98, 1479 (1955); 10.1103/PhysRev.98.1479 Web of Science®Google Scholar R. B. Dingle, Philos. Mag. 40, 573 (1949). 10.1080/14786444908521743 Web of Science®Google Scholar 13 F. Mentch and J. B. Anderson, J. Chem. Phys. 80, 2675 (1984). 10.1063/1.447063 CASWeb of Science®Google Scholar 14 D. M. Ceperley and B. J. Alder, J. Chem. Phys., to appear. Google Scholar Citing Literature Volume26, IssueS18Supplement: Atomic, Molecular and Solid‐State Theory, and Computational Quantum Chemistry1/15 March 1984Pages 709-717 ReferencesRelatedInformation
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