Anionic and Neutral States of LiJO - PDF document

1 8326 Phys. Chem. Anionic and Neutral S
8326 Phys. Chem. Anionic and Neutral States of LiJO Jack Simons. Chemistry Department, Utah, Salt Received: January cation, three initio techniques. were determined single-excitation configuration interaction method. Electron energies for I. Introduction Recent theoretical studies indicate radicals containing alkali metal atoms can accommodate more simple alkali metal oxide and theoretical4 alkali metal trimer anions isomer. Recently, The neutral studied both experimentally7 et al. Knudsen effusion mass lithium oxidee7 atomization energy dissociation energy produce Li for Li3O(g) molecule with Early predictions advanced calculationsl0J3 similar to and vertical ionization potential and 3.45 correspondence should Present address: 650 Harry Road, San Jose, CA 95120-6099. 0022-365419412098-8326%04.50/0 although the theoretical dissociation kcal/mol10 agrees neither the anionic states experimentally studied. 11. Computational Aspects lithium atom, Dunning (9s5p/3s2p) same exponent and one explored within complete active formalism as second-order Mdler-Plesset molecular orbitals result from atomic orbitals doubly occupied core-core and correlation effects negligible for atoms due to remaining eight (cation), ten (anion) electrons inapplicable for excited electronic states, single-excitation con- figuration interaction to determine geometry and relative energy 1994 American Chemical Society and Neutral Stationary Points Harmonic Frequencies Different Electronic Cation, Neutral, The Journal Physical Chemistry, Lit0 Li30 Li30 Li'O Li30 Li@- Li$J LiO Li@- 'E' (+)3c' 'Bz (+))bz 2'A1 (+)7a, 'Ai (+)2az" IAl' (+)4af2 'E' (+)4a(3d 'AI (+)6a17a1 species symmetry state DEC method geometry vibrational freqvenciesb (R') EQCI L

2 i,O+ Dlh 'AI' (+) CAS R = 1.726 a'
i,O+ Dlh 'AI' (+) CAS R = 1.726 a'" 244, e' 265, a,' 655. d 806 91 0.0 MP? R = 1 7nR 767 141 -3.593 . ... - . . . . . __ CAS R= 1.707 MP2 R= 1.694 'AI' (+)4al' CAS R= 1.696 CAS RI = 1.705 RZ = 1.707 4 = 114.58 MP2 RI = 1.690 R2 = 1.707 4 = 114.96 CIS R, = 1.662 RZ = 1.699 4 = 117.96 CIS RI= 1.718 R2= 1.671 4 = 121.08 CAS R= 1.706 MP2 R= 1.697 CAS R= 1.708 MP2 R= 1.697 CAS R= 1.693 CAS RI = 1.709 RZ = 1.707 4 = 131.18 MP2 R,= 1.717 Rt = 1.697 4 = 129.23 CAS RI = 1.700 RZ = 1.707 4 = 109.43 MP2 R, = 1.692 RZ = 1.709 4 = 109.81 not a stationary point 153 -2.856 bl 193,bz215,a1219,a,679,a~801,bz871 153 -2.890 bz 202 (9250). a1 213 (87). bl 243 (I), a, 687 (52). b844 (148). al 849 (16) b, 210, bz 229, a, 244, a, 697, bz 814, a1 903 bz 132i. bl21 I. al 424. a, 702. bz 745, a, IO25 -2.854= (77),az"172(179),a,'693 (O),d856(214) 254 -3.960 144, b, 149, bz IO1 (123). bl 202 (166),al 235 (316), a, 682 (5). b 806 (781). a! 875 (458) bz 270i. bl 144. a1 191, a1 673, a1 761. b 809 246 4.024 bz 154i (6108), a, I76 (342), b, 200 (162). a, 682 (139), a, 824 (439), bz 845 (318) presented. The electronic charge The dominant electronic configurations parentheses. The considered cautiously. In approach, creation spin eigenstates witha UHFreference. handle these doublet cases, also correlates with for which straightforwardly applicable. the MP2 geometry optimizations core orbitals. In general, the structures MP2levels. whichsuggests correlation effects geometries, but it is inappropriate accurately compareenergies electrons. Hence, quadraticconfiguration interaction determine relative energies into account dynamical correlation effects. In core electrons uncorrelated. checked in such a restriction changes detachment energy The QCI Gaussian 92

3 stationary points potential energy surf
stationary points potential energy surfaces cation, neutral, and anion determined Li , Li Liz Figore 1. Geometrical parametersfor theCt.structureoftheLi~Oneutral and anionic species. and thegeometrical parameters vibrational frequencies derivatives. For neutral, stationary relative energies were obtained the QCISD(T) energies (VDE) electronafIinities(E&) presentedinTables relative energies Cation and electronic configuration this la- frequencies for quite similar 8328 The Journal of Physical Chemistry, Vol. 98, No. 34, 1994 Gutowski and Simons Vertical Electron Adiabatic Ionization Ionization )(in eV) Calculated transition VIP IP. 'AI'+ e- - 'A( 3.603 3.593 'AI +e-- 'Bz 2.933 2.890 IAl +e-- Z2A10 2.954 2.909 !A( + e-- ZA 1 2.052 2.042 estimated as Vertical Electron Detachment Energies (VDE) Adiabatic Electron Alfinities the QCISD(T) transition VDE EA. 'A,' + e- - 'AI' 0.656 0.656 I'AI + c- ]AI 0.450 0.430 AI + c- ]AI 1.346' 1.074a I'AI + e-- IBz 0.459 0.431 'B2 + e- - 3B1 1.151 1.134 estimated as -4 Li3U 'E'(+)443e' Li3D 'A;(+)44' t I I n ?I t Relative energies electron detachment the vertical the ground- cation H]O+, studied earlier,2s cation. Because function is found accurate. Unexpectedly, vibrational mode has an imaginary frequency Doubting whether imaginary frequency search for Hence, weconclude genuine minimum, and symmetry-breaking artifacts." the MP2 frequencies of 3 2 Graph representing pseudorotation for The intermediate underlying cation easily accessible the neutral interact constructively small s-type contributions from the central observed in Mulliken population atomic charges and -0.60 ionization potentials Li30+(lA;) +e-) 3.60and IPS agreement with electron propagator theory estimation of al

4 kali metal atoms, result support claimed
kali metal atoms, result support claimed "superalkali" the neutral symmetry has distortion. Geometry optimization MPZgeometries and frequencies similar. Due geometry optimization for of this 'E'state tested on point characteristics were found similar for the Li(z)-Li(~) the bz the other orbital the destructive. These reaction path. energy difference symmetry specified consistent calculation of and Neutral States The Journal obtained within found is 0.04 eV. vertical excitation would be conical intersection. reflected in might be studied ionization techniques.28 next excited has ZAP is somewhat shorter. These features consistent with similar trends alkali metal unpaired electron with constructive vertical excitation energy is 1.55 Li30- has and that a significant out-of-plane vibrational MP2 and predict a quite similar function for anionic lAl’ (+)4a1’2 configuration, but contributions from important and 0.30 each. This consistent with neutral (0.7 also electronically 0.656 eV, peak is neutral equilibrium In addition to a second points develop The structures anionic stationary 7al for to the discussed above. and the eV. Both approaches locate with negative be extremely the QCISD(T) 0.001 eV, whereas order. Clearly, 3, is ground 2Al’ lie in 0.43-0.46 eV. higher pseudorotating that the experimental detection, a significant experimental studies (corrected for vibrations) for thedecomposition cation, neutral, 84.40, 44.54, increased stability electron affinity larger for Li30 than for Li. energy for IV. Conclusions Theoretical calculations indicate electronically bound. cation, ground-state the MP2 with respect 1.1 eV, respectively. geometrical features daughter-state 3A1 or antibonding interactions among to the respective an

5 ion state’s 0.002 eV. Hence, and Z
ion state’s 0.002 eV. Hence, and ZAP ground state. pseudorotates through with a vertical excitation with a ground-state neutral easily accessible and adiabatic potentials for 3.59 eV, respectively, species discussed neutral and more amenable experimental studies their hydrogen-substituted analogs HsO-, which two bound and Li30 results for the VDE eV, whereas require ca. work was Naval Research Science Foundation References and Notes (1) Bauschlicher, Jr., C. W.;Partridge, H.; Pettersson,L.G. M. J. Chem. Phys. 1993, 99, 3654. Plenum Press: (3) Sarkas, H. W.; Arnold, S. T.; Hendricks, J. H.; Bowen, K. H. Manuscript in preparation. (4) Bonacic-Koutecky, V.; Fantucci, P.; Koutecky, J. Chem. Reu. 1991, Chem. Phys., H. R. Chem. Phys. Schleyer, P. Wurthwein, E.-U.; Pople, 8330 34, 1994 Gutowski and Simons Gutsev, G. Chem. Phys. 1982, 92, 262. E.; Boldyrev, A. Schleyer, P. Niessen, W.; Schleyer, P. Kudo, H.; Wu, C. Chem. Express Schleyer, P. Unpublished results. Chandrasekhar, J.; Spitznagel, 1977, 66, 879. 1993, 98, Utah MESS-KIT a suite highly modular programmed in-house to Nichols, M. R. Hoffmann, R. L. Taylor, M. Gutowski, Wang, M. Feyereisen, and J.; Taylor, H.; Schmidt, P.; J.; Jorgensen, P.; Taylor, H.; Ozment, Phys. Chem. 89, 52. C. J.; Miller, W. Chem. Phys. 1984, 106, 6973. Comput. Chem. Yeager, D. Chem. Phys. Head-Gordon, M.; Pople, A.; Frisch, M. 1992, 96, Frisch, M. M.; Gill, P. M.; Wong, M. W.; Foresman, Robb, M. Gonzales, C.; Martin, R. D. J.; DeFrees, D. Baker, J.; J. J. Pittsburgh, PA, Private communication. Head-Gordon, M.; Chem. Phys. 1987,87, 5968. Chem. Phys. 91, 669. Raine, G. P.; Schaefer, H. Dupuis, M. Allen, W. Chem. Phys. R.; Borden, Phys. Chem. J.; Kobe, Manz, J.; Phys. Chem. Gutowski, M.; Simons,