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Henry F. Schaefer - One of the best experts on this subject based on the ideXlab platform.
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intermolecular interactions and proton transfer in the hydrogen halide superoxide anion complexes
Physical Chemistry Chemical Physics, 2016Co-Authors: Sebastian J. R. Lee, Wayne J Mullinax, Henry F. SchaeferAbstract:The superoxide radical anion O2(-) is involved in many important chemical processes spanning different scientific disciplines (e.g., environmental and biological sciences). Characterizing its interaction with various substrates to help elucidate its rich chemistry may have far reaching implications. Herein, we investigate the interaction between O2(-) (X[combining tilde] (2)Πg) and the hydrogen halides (X[combining tilde] (1)Σ) with coupled-cluster theory. In contrast to the short (1.324 A) hydrogen bond formed between the HF and O2(-) monomers, a barrierless proton transfer occurs for the heavier hydrogen halides with the resulting complexes characterized as long (>1.89 A) hydrogen bonds between halide anions and the HO2 radical. The dissociation Energy with harmonic Zero-Point Vibrational Energy (ZPVE) for FHO2(-) (X[combining tilde] (2)A'') → HF (X[combining tilde] (1)Σ) + O2(-) (X[combining tilde] (2)Πg) is 31.2 kcal mol(-1). The other dissociation energies with ZPVE for X(-)HO2 (X[combining tilde] (2)A'') → X(-) (X[combining tilde] (1)Σ) + HO2 (X[combining tilde] (2)A'') are 25.7 kcal mol(-1) for X = Cl, 21.9 kcal mol(-1) for X = Br, and 17.9 kcal mol(-1) for X = I. Additionally, the heavier hydrogen halides can form weak halogen bonds H-XO2(-) (X[combining tilde] (2)A'') with interaction energies including ZPVE of -2.3 kcal mol(-1) for HCl, -8.3 kcal mol(-1) for HBr, and -16.7 kcal mol(-1) for HI.
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thermochemistry of the hoso radical a key intermediate in fossil fuel combustion
Journal of Physical Chemistry A, 2009Co-Authors: Steven E Wheeler, Henry F. SchaeferAbstract:Despite the key role of the HOSO radical in the combustion of sulfur-rich fuels, the thermochemistry of this simple species is not well-established. Due to the extraordinary sensitivity of the potential Energy surface to basis set and electron correlation methods in ab initio computations, there is no consensus in the literature regarding the structure of the global minimum syn-HOSO. A definitive enthalpy of formation for HOSO is presented, based on systematically extrapolated ab initio energies, accounting for electron correlation primarily through coupled cluster theory, including up to single, double, and triple excitations with a perturbative correction for connected quadruple excitations [CCSDT(Q)]. These extrapolated valence electronic energies have been corrected for core−electron correlation, harmonic and anharmonic Zero-Point Vibrational Energy, and non-Born−Oppenheimer and scalar relativistic effects. Our final recommended enthalpy of formation is ΔfH0°(syn-HOSO) = −58.0 kcal mol−1. The planar a...
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mono and dibridged isomers of si2h3 and si2h4 the true ground state global minima theory and experiment in concert
Journal of the American Chemical Society, 2003Co-Authors: Levent Sari, Henry F. Schaefer, Michael C Mccarthy, P ThaddeusAbstract:Highly correlated ab initio coupled-cluster theories (e.g., CCSD(T), CCSDT) were applied on the ground electronic states of Si2H3 and Si2H4, with substantive basis sets. A total of 10 isomers, which include mono- and dibridged structures, were investigated. Scalar relativistic corrections and Zero-Point Vibrational Energy corrections were included to predict reliable energetics. For Si2H3, we predict an unanticipated monobridged H2Si−H−Si-like structure (Cs, 2A‘ ‘) to be the lowest Energy isomer, in constrast to previous studies which concluded that either H3Si−Si (Cs, 2A‘ ‘) or near-planar H2Si−SiH (C1, 2A) is the global minimum. Our results confirm that the disilene isomer, H2Si−SiH2, is the lowest Energy isomer for Si2H4 and that it has a trans-bent structure (C2h, 1Ag). In addition to the much studied silylsilylene, H3Si−SiH, we also find that a new monobridged isomer H2Si−H−SiH (C1, 1A, designated 2c) is a minimum on the potential Energy surface and that it has comparable stability; both isomers are ...
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electron affinities of the oxides of aluminum silicon phosphorus sulfur and chlorine
Journal of Chemical Physics, 1999Co-Authors: Nicole R Brinkmann, Gregory S Tschumper, Henry F. SchaeferAbstract:The adiabatic electron affinities of five second row atoms (Al, Si, P, S, Cl) and their monoxides and dioxides were determined using six different density functional or hybrid Hartree–Fock/density functional methods. The 15 species selected form a convenient closed set for which reliable experimental electron affinities exist for 13 of the species. Zero-Point Vibrational Energy corrected electron affinities are also reported. Equilibrium geometries and Vibrational frequencies were determined with each density functional method. The method based on the Becke exchange functional and the Lee–Yang–Parr correlation (BLYP) functional reproduced the experimental electron affinities most accurately, having an average absolute error of 0.15 eV. Using this functional, the electron affinities were predicted for SiO and SiO2, molecules for which electron affinities are not known experimentally, as 0.11 eV and 2.03 eV, respectively. It is concluded that the accuracy observed for density functional theory methods appli...
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predicting electron affinities with density functional theory some positive results for negative ions
Journal of Chemical Physics, 1997Co-Authors: Gregory S Tschumper, Henry F. SchaeferAbstract:The atomic electron affinities of the eight first row (H,Li,…,F) atoms as well as the adiabatic electron affinities of 12 first row diatomic and 15 first row triatomic molecules were determined using six different density functional or hybrid Hartree–Fock/density functional methods. The 35 species were selected for having relatively well-established experimental electron affinities. Harmonic Zero-Point Vibrational Energy corrected electron affinities are also reported for the diatomic and triatomic molecules. Equilibrium geometries and harmonic Vibrational frequencies are given for the 27 molecules and their anions as determined with each density functional method. Discussion focuses on comparison of theoretical and experimental electron affinities. For the atomic, diatomic, and triatomic electron affinities the average absolute error is reported for each exchange–correlation functional. Since many of the molecular anion structures and Vibrational frequencies are unknown, the work suggests new experimental directions.
Odile R. Smits - One of the best experts on this subject based on the ideXlab platform.
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the lennard jones potential revisited analytical expressions for Vibrational effects in cubic and hexagonal close packed lattices
Journal of Physical Chemistry A, 2021Co-Authors: Peter Schwerdtfeger, Antony Burrows, Odile R. SmitsAbstract:Analytical formulas are derived for the Zero-Point Vibrational Energy and anharmonicity corrections of the cohesive Energy and the mode Gruneisen parameter within the Einstein model for the cubic l...
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the lennard jones potential revisited analytical expressions for Vibrational effects in cubic and hexagonal close packed lattices
Journal of Physical Chemistry A, 2021Co-Authors: Peter Schwerdtfeger, Antony Burrows, Odile R. SmitsAbstract:Analytical formulas are derived for the Zero-Point Vibrational Energy and anharmonicity corrections of the cohesive Energy and the mode Gruneisen parameter within the Einstein model for the cubic lattices (sc, bcc, and fcc) and for the hexagonal close-packed structure. This extends the work done by Lennard-Jones and Ingham in 1924, Corner in 1939, and Wallace in 1965. The formulas are based on the description of two-body Energy contributions by an inverse power expansion (extended Lennard-Jones potential). These make use of three-dimensional lattice sums, which can be transformed to fast converging series and accurately determined by various expansion techniques. We apply these new lattice sum expressions to the rare gas solids and discuss associated critical points. The derived formulas give qualitative but nevertheless deep insight into Vibrational effects in solids from the lightest (helium) to the heaviest rare gas element (oganesson), both presenting special cases because of strong quantum effects for the former and strong relativistic effects for the latter.
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The Lennard Jones Potential Revisited -- Analytical Expressions for Vibrational Effects in Cubic and Hexagonal Close-Packed Lattices.
arXiv: Materials Science, 2020Co-Authors: Peter Schwerdtfeger, Antony Burrows, Odile R. SmitsAbstract:Analytical formulae are derived for the Zero-Point Vibrational Energy and anharmonicity corrections of the cohesive Energy and the mode Gruneisen parameter within the Einstein model for the cubic lattices (sc, bcc and fcc) and for the hexagonal close-packed structure. This extends the work done by Lennard Jones and Ingham in 1924, Corner in 1939 and Wallace in 1965. The formulae are based on the description of two-body Energy contributions by an inverse power expansion (extended Lennard-Jones potential). These make use of three-dimensional lattice sums, which can be transformed to fast converging series and accurately determined by various expansion techniques. We apply these new lattice sum expressions to the rare gas solids and discuss associated critical points. The derived formulae give qualitative but nevertheless deep insight into Vibrational effects in solids from the lightest (helium) to the heaviest rare gas element (oganesson), both presenting special cases because of strong quantum effects for the former and strong relativistic effects for the latter.
Peter Schwerdtfeger - One of the best experts on this subject based on the ideXlab platform.
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the lennard jones potential revisited analytical expressions for Vibrational effects in cubic and hexagonal close packed lattices
Journal of Physical Chemistry A, 2021Co-Authors: Peter Schwerdtfeger, Antony Burrows, Odile R. SmitsAbstract:Analytical formulas are derived for the Zero-Point Vibrational Energy and anharmonicity corrections of the cohesive Energy and the mode Gruneisen parameter within the Einstein model for the cubic l...
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the lennard jones potential revisited analytical expressions for Vibrational effects in cubic and hexagonal close packed lattices
Journal of Physical Chemistry A, 2021Co-Authors: Peter Schwerdtfeger, Antony Burrows, Odile R. SmitsAbstract:Analytical formulas are derived for the Zero-Point Vibrational Energy and anharmonicity corrections of the cohesive Energy and the mode Gruneisen parameter within the Einstein model for the cubic lattices (sc, bcc, and fcc) and for the hexagonal close-packed structure. This extends the work done by Lennard-Jones and Ingham in 1924, Corner in 1939, and Wallace in 1965. The formulas are based on the description of two-body Energy contributions by an inverse power expansion (extended Lennard-Jones potential). These make use of three-dimensional lattice sums, which can be transformed to fast converging series and accurately determined by various expansion techniques. We apply these new lattice sum expressions to the rare gas solids and discuss associated critical points. The derived formulas give qualitative but nevertheless deep insight into Vibrational effects in solids from the lightest (helium) to the heaviest rare gas element (oganesson), both presenting special cases because of strong quantum effects for the former and strong relativistic effects for the latter.
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The Lennard Jones Potential Revisited -- Analytical Expressions for Vibrational Effects in Cubic and Hexagonal Close-Packed Lattices.
arXiv: Materials Science, 2020Co-Authors: Peter Schwerdtfeger, Antony Burrows, Odile R. SmitsAbstract:Analytical formulae are derived for the Zero-Point Vibrational Energy and anharmonicity corrections of the cohesive Energy and the mode Gruneisen parameter within the Einstein model for the cubic lattices (sc, bcc and fcc) and for the hexagonal close-packed structure. This extends the work done by Lennard Jones and Ingham in 1924, Corner in 1939 and Wallace in 1965. The formulae are based on the description of two-body Energy contributions by an inverse power expansion (extended Lennard-Jones potential). These make use of three-dimensional lattice sums, which can be transformed to fast converging series and accurately determined by various expansion techniques. We apply these new lattice sum expressions to the rare gas solids and discuss associated critical points. The derived formulae give qualitative but nevertheless deep insight into Vibrational effects in solids from the lightest (helium) to the heaviest rare gas element (oganesson), both presenting special cases because of strong quantum effects for the former and strong relativistic effects for the latter.
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extension of the lennard jones potential theoretical investigations into rare gas clusters and crystal lattices of he ne ar and kr using many body interaction expansions
Physical Review B, 2006Co-Authors: Peter Schwerdtfeger, Nicola Gaston, Robert P Krawczyk, Ralf Tonner, Gloria E MoyanoAbstract:The many-body expansion ${V}_{\mathrm{int}}={\ensuremath{\sum}}_{ilj}{V}^{(2)}({r}_{ij})+{\ensuremath{\sum}}_{iljlk}{V}^{(3)}({r}_{ij},{r}_{ik},{r}_{jk})+\ensuremath{\cdots},$ in terms of interaction potentials between rare-gas atoms converges fast at distances $rg{r}_{\mathit{HS}}$, with ${r}_{\mathit{HS}}$ being the hard-sphere radius at the start of the repulsive wall of the interaction potential. Hence, for the solid state where the minimum distance is always above ${r}_{\mathit{HS}}$, a reasonable accuracy is already obtained for the lattice parameters and cohesive energies of the rare-gas elements using precise two-body terms. All tested two-body potentials show a preference of the hcp over the fcc structure. We demonstrate that this is always the case for the Lennard-Jones potential. We extend the Lennard-Jones potential to obtain analytical expressions for the lattice parameters, cohesive Energy, and bulk modulus using the solid-state parameters of Lennard-Jones and Ingham [Proc. R. Soc. London, Ser. A 107, 636 (1925)], which we evaluate up to computer precision for the cubic lattices and hcp. The inclusion of three-body terms does not change the preference of hcp over fcc, and Zero-Point Vibrational effects are responsible for the transition from hcp to fcc as shown recently by Rosciszewski et al. [Phys. Rev. B 62, 5482 (2000)]. More precisely, we show that it is the coupling between the harmonic modes which leads to the preference of fcc over hcp, as the simple Einstein approximation of moving an atom in the static field of all other atoms fails to describe this difference accurately. Anharmonicity corrections to the crystal stability are found to be small for argon and krypton. We show that at pressures higher than $15\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ three-body effects become very important for argon and good agreement is reached with experimental high-pressure density measurements up to $30\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, where higher than three-body effects become important. At high pressures we find that fcc is preferred over the hcp structure. Zero-Point Vibrational effects for the solid can be successfully estimated from an extrapolation of the cluster Zero-Point Vibrational energies with increasing cluster size $N$. For He, the harmonic Zero-Point Vibrational Energy is predicted to be always above the potential Energy contribution for all cluster sizes up to the solid state at structures obtained from the two-body force. Here anharmonicity effects are very large which is typical for a quantum solid.
Kaichung Lau - One of the best experts on this subject based on the ideXlab platform.
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high level ab initio predictions for the ionization Energy bond dissociation energies and heats of formation of vanadium methylidyne radical and its cation vch vch
Journal of Physical Chemistry A, 2019Co-Authors: Chowshing Lam, Kaichung LauAbstract:The ionization Energy (IE) of VCH, the 0 K V–CH/VC–H bond dissociation energies (D0s), and the heats of formation at 0 K (ΔHf0°) and 298 K (ΔHf298°) for VCH/VCH+ are predicted by the wave function-based CCSDTQ/CBS approach. This composite-coupled cluster method includes full quadruple excitations in conjunction with the approximation to the complete basis set (CBS) limit. The contributions of Zero-Point Vibrational Energy, core–valence (CV) correlation, spin–orbit coupling, and scalar relativistic corrections are taken into account. The present calculations show that adiabatic IE(VCH) = 6.785 eV and demonstrate excellent agreement with an IE value of 6.774 7 ± 0.000 1 eV measured with two-color laser-pulsed field ionization-photoelectron spectroscopy. The CCSDT and MRCI+Q methods which include CV correlations give the best predictions of harmonic frequencies: ω2 (ω2+) (bending) = 534 (650) and 564 (641) cm–1 and the V–CH stretching ω3 (ω3+) = 835 (827) and 856 (857) cm–1 compared with the experimental val...
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high level ab initio predictions for the ionization Energy electron affinity and heats of formation of cyclopentadienyl radical cation and anion c5h5 c5h5 c5h5
Journal of Physical Chemistry A, 2014Co-Authors: Kaichung LauAbstract:The ionization Energy (IE), electron affinity (EA), and heats of formation (ΔH°f0/ΔH°f298) for cyclopentadienyl radical, cation, and anion, C5H5/C5H5+/C5H5–, have been calculated by wave function-based ab initio CCSDT/CBS approach, which involves approximation to complete basis set (CBS) limit at coupled-cluster level with up to full triple excitations (CCSDT). The Zero-Point Vibrational Energy correction, core–valence electronic correction, scalar relativistic effect, and higher-order corrections beyond the CCSD(T) wave function are included in these calculations. The allylic [C5H5(2A2)] and dienylic [C5H5(2B1)] forms of cyclopentadienyl radical are considered: the ground state structure exists in the dienyl form and it is about 30 meV more stable than the allylic structure. Both structures are lying closely and are interconvertible along the normal mode of b2 in-plane vibration. The CCSDT/CBS predictions (in eV) for IE[C5H5+(3A1′)←C5H5(2B1)] = 8.443, IE[C5H5+(1A1)←C5H5(2B1)] = 8.634 and EA[C5H5–(1A1′)←C...
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high level ab initio predictions for the ionization Energy bond dissociation energies and heats of formation of nickel carbide nic and its cation nic
Journal of Chemical Physics, 2010Co-Authors: Kaichung Lau, Yih Chung Chang, Xiaoyu ShiAbstract:The ionization Energy (IE) of CoC and the 0 K bond dissociation energies (D0) and the heats of formation at 0 K (ΔH°f0) and 298 K (ΔH°f298) for CoC and CoC(+) are predicted by the wavefunction based coupled-cluster theory with single, double, triple and quadruple excitations (CCSDTQ) and complete basis set (CBS) approach. The CCSDTQ∕CBS calculations presented here involve the approximation to the CBS limit at the coupled cluster level up to full quadruple excitations along with the Zero-Point Vibrational Energy, high-order correlation, core-valence (CV) electronic, spin-orbit coupling, and scalar relativistic effect corrections. The present calculations provide the correct symmetry, (1)Σ(+), for the ground state of CoC(+). The CCSDTQ∕CBS IE(CoC) = 7.740 eV is found in good agreement with the experimental IE value of 7.73467 ± 0.00007 eV, determined in a two-color laser photoion and pulsed field ionization-photoelectron study. This work together with the previous experimental and theoretical investigations support the conclusion that the CCSDTQ∕CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC, CoC, and NiC. Among the single-reference based coupled-cluster methods and multi-reference configuration interaction (MRCI) approach, the CCSDTQ and MRCI methods give the best predictions to the harmonic frequencies ωe (ωe (+)) = 956 (992) and 976 (1004) cm(-1) and the bond lengths re (re (+)) = 1.560 (1.528) and 1.550 (1.522) A, respectively, for CoC (CoC(+)) in comparison with the experimental values. The CCSDTQ∕CBS calculations give the prediction of D0(Co(+)-C) - D0(Co-C) = 0.175 eV, which is also consistent with the experimental determination of 0.14630 ± 0.00014 eV. The theoretical results show that the CV and valence-valence electronic correlations beyond CCSD(T) wavefunction and the relativistic effect make significant contributions to the calculated thermochemical properties of CoC∕CoC(+). For the experimental D0 and ΔH(o) f0 values of CoC∕CoC(+), which are not known experimentally, we recommend the following CCSDTQ∕CBS predictions: ΔH(o) f0(CoC) = 775.7 kJ∕mol and ΔH(o) f0(CoC(+)) = 1522.5 kJ∕mol, ΔH(o) f298(CoC) = 779.2 kJ∕mol and ΔH(o) 298(CoC(+)) = 1526.0 kJ∕mol.
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high level ab initio predictions for the ionization Energy bond dissociation energies and heats of formations of iron carbide fec and its cation fec
Journal of Physical Chemistry A, 2009Co-Authors: Kaichung Lau, Yih Chung Chang, Chowshing LamAbstract:The ionization Energy IE of NiC and the 0 K bond dissociation energies D0 and heats of formation at 0 K H o f0 and 298 K H o f298 for NiC and NiC + are predicted by the wavefunction based CCSDTQFull/CBS approach and the multireference configuration interaction MRCI method with Davidson correction MRCI+Q. The CCSDTQFull/CBS calculations presented here involve the approximation to the complete basis set CBS limit at the coupled cluster level up to full quadruple excitations along with the Zero-Point Vibrational Energy ZPVE, high-order correlation, core-valence electronic CV, spin-orbit coupling SO, and scalar relativistic effect SR corrections. The present calculations provide the correct symmetry predictions for the ground states of NiC and NiC + to be 1+ and 2+ , respectively. The CCSDTQFull/CBS IENiC =8.356 eV is found to compare favorably with the experimental IE value of 8.372 050.000 06 eV. The predicted IENiC value at the MRCI+Q /cc-pwCV5Z level, including the ZPVE, SO, and SR effects is 8.00 eV, which is 0.37 eV lower than the experimental value. This work together with the previous experimental and theoretical investigations supports the conclusion that the CCSDTQFull/CBS method is capable of providing reliable IE predictions for 3d-transition metal carbides, such as FeC and NiC. Furthermore, the CCSDTQFull/CBS
Toshio Kasai - One of the best experts on this subject based on the ideXlab platform.
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location of hydrogen adsorbed on rh 111 studied by low Energy electron diffraction and nuclear reaction analysis
Physical Review B, 2007Co-Authors: Masayuki Fukuoka, Shouhei Ogura, Masuaki Matsumoto, Katsuyuki Fukutani, Michio Okada, Toshio KasaiAbstract:The structures of clean and hydrogen-adsorbed Rh(111) surfaces were investigated by dynamical low-Energy electron-diffraction (LEED) analysis. Exposure of ${\mathrm{D}}_{2}$ induced no additional LEED patterns except for $(1\ifmmode\times\else\texttimes\fi{}1)$. Surface-layer relaxation occurs vertically on both clean and D-saturated surfaces. On the clean surface, the interlayer distance between the first and second layers $({d}_{12})$ is smaller by $1.2(\ifmmode\pm\else\textpm\fi{}0.6)%$ than the corresponding bulk distance of $2.194\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. On the other hand, the contraction of ${d}_{12}$ is removed on the D-saturated surface. Detailed LEED analysis demonstrates that the D atoms are adsorbed on the fcc threefold hollow sites. The absolute saturation coverage of H on Rh(111) was determined to be 0.84 ML by nuclear reaction analysis (NRA). Moreover, the Zero-Point Vibrational Energy of H was derived from the analysis of the NRA resonance profile, which is discussed in comparison with the results of high-resolution electron-Energy-loss spectroscopy.
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Location of hydrogen adsorbed on Rh(111) studied by low-Energy electron diffraction and nuclear reaction analysis
Physical Review B - Condensed Matter and Materials Physics, 2007Co-Authors: Masayuki Fukuoka, Shouhei Ogura, Masuaki Matsumoto, Katsuyuki Fukutani, Michio Okada, Toshio KasaiAbstract:The structures of clean and hydrogen-adsorbed Rh111 surfaces were investigated by dynamical low-Energy electron-diffraction LEED analysis. Exposure of D2 induced no additional LEED patterns except for 11. Surface-layer relaxation occurs vertically on both clean and D-saturated surfaces. On the clean surface, the interlayer distance between the first and second layers d12 is smaller by 1.2�0.6% than the corresponding bulk distance of 2.194 �. On the other hand, the contraction of d12 is removed on the D-saturated surface. Detailed LEED analysis demonstrates that the D atoms are adsorbed on the fcc threefold hollow sites. The absolute saturation coverage of H on Rh111 was determined to be 0.84 ML by nuclear reaction analysis NRA. Moreover, the Zero-Point Vibrational Energy of H was derived from the analysis of the NRA resonance profile, which is discussed in comparison with the results of high-resolution electron-Energy-loss spectroscopy.
