Depth Of De Research Articles

Full empirical potential curves for the X(1)Σ(+) and A(1)Π states of CH(+) from a direct-potential-fit analysis.

All available "conventional" absorption/emission spectroscopic data have been combined with photodissociation data and translational spectroscopy data in a global analysis that yields analytic potential energy and Born-Oppenheimer breakdown functions for the X(1)Σ(+) and A(1)Π states of CH(+) and its isotopologues that reproduce all of the data (on average) within their assigned uncertainties. For the ground X(1)Σ(+) state, this fully quantum mechanical "Direct-Potential-Fit" analysis yielded an improved empirical well depth of 𝔇e = 34 362.8(3) cm(-1) and equilibrium bond length of re = 1.128 462 5 (58) Å. For the A(1)Π state, the resulting well depth and equilibrium bond length are 𝔇e = 10 303.7(3) cm(-1) and re = 1.235 896 (14) Å, while the electronic isotope shift from the hydride to the deuteride is ΔTe = - 5.99(±0.08) cm(-1).

Dissociation energies and potential energy functions for the ground X (1)Σ(+) and "avoided-crossing" A (1)Σ(+) states of NaH.

A direct-potential-fit analysis of all accessible data for the A (1)Σ(+) - X (1)Σ(+) system of NaH and NaD is used to determine analytic potential energy functions incorporating the correct theoretically predicted long-range behaviour. These potentials represent all of the data (on average) within the experimental uncertainties and yield an improved estimate for the ground-state NaH well depth of 𝔇e = 15797.4 (±4.3) cm(-1), which is ∼20 cm(-1) smaller than the best previous estimate. The present analysis also yields the first empirical determination of centrifugal (non-adiabatic) and potential-energy (adiabatic) Born-Oppenheimer breakdown correction functions for this system, with the latter showing that the A-state electronic isotope shift is -1.1(±0.6) cm(-1) going from NaH to NaD.

Theoretical Study of the vdW Complex Cd···N2

The supermolecular CCSD(T) ab initio calculations of potential energy surface for the electronic ground state of van der Waals complex formed from a cadmium atom and a nitrogen molecule are presented. Our calculations indicate the bent orientation (Jacobi coordinates are rN-N = 1.10 Å, R = 4.53 Å, angle θ = 62°) of the van der Waals (vdW) system with a well depth of De = 73.3 cm-1. This well depth was shifted to the value of 76.7 cm-1 by systematical extension of mid-bond functions. The temperature dependences of the theoretical coefficient of diffusion were evaluated from the molecular dynamics and the Enskog-Chapman theory. The theoretical values at 273 K are compared with the available experimental data.

Theoretical Study of H2...I- van der Waals Anion Complex

The ab initio potential energy surface (PES) for the weak interaction of hydrogen molecule with iodine anion is presented. The surface was obtained by the supermolecular method at the MP4(SDTQ) level of theory. Our calculations indicate the van der Waals (vdW) system for the linear configuration at rH-H = 0.752 Å and R = 3.76 Å with a well depth of De = 2096 μEh. The presented PES reveals also a transition state for the perpendicular arrangement at rH-H = 0.7416 Å and R = 4.63 Å with an interaction energy of -113 μEh. The physical origin of stability of the vdW H2...I- structure with respect to the H2...X- (X = F, Cl, Br) one was analysed by the symmetry adapted perturbation theory (SAPT) based on the single determinant HF wave function. The separation of the interaction energy shows that the dispersion forces play a much more important role for the systems with Cl, Br and I than for H2...F- and their importance slightly increases in the order Cl < Br < I. The global importance of the electrostatic and the induction energies decreases in the order F > Cl > Br > I.

On the structure and physical origin of the interaction in H(2) ... Cl(-) and H(2) ... Br(-) van der Waals anion complexes.

The ab initio three-dimensional potential energy surface (PES) for the weak interaction of hydrogen molecule with bromine anion is presented. The surface was obtained by the supermolecular method at the coupled cluster with single and double excitations and noniterative correction to triple excitations (CCSD(T)) level of theory. Our calculations indicate the van der Waals (vdW) system for the linear orientation at R=3.37 A with a well depth of D(e)=660.1 cm(-1). The presented PES reveals also transition state for the perpendicular orientation at R=4.22 A with a barrier of 607.1 cm(-1). The physical origin of the stability of vdW H(2) ... Br(-) structure with respect to the H(2) ... Cl(-) one was analyzed by the symmetry adapted perturbation theory based on the single determinant Hartree-Fock (HF) wave function. The separation of the interaction energy shows that the dispersion forces play slightly more important role in the stabilization of the vdW system with Br(-) than with Cl(-).

On the Structure and Physical Origin of the Weak Interaction Between H and CO

The adiabatic potential energy surface of the H-CO complex in the van der Waals region, described by Jacobi coordinates (r = 1.128 Å, R, Θ), was investigated using the supermolecular coupled-clusters CCSD(T) method. Our calculations indicate a minimum for bent arrangements. It was found on the carbon side of CO molecule at R = 3.6 Å (Θ = 76°) with a well depth of De = -156.5 μEh. The saddle points are localised at linear conformations for R = 4.37 Å (Θ = 0°) and R = 3.91 Å (Θ = 180°). The physical origin of the studied interaction was analysed by the intermolecular perturbation theory based on the single-determinant unrestricted Hartree-Fock wave function. The separation of the interaction energies shows that the locations of the predicted stable bent structure is primarily determined by delicate balance between the repulsive Heitler-London and attractive dispersion and induction energy components.

Nature of interaction energy anisotropy in the Li(2S)–HF (˜X1Σ+) van der Waals complex. A theoretical study

The potential-energy surface for the Li(2S)–HF (˜ X1Σ+ interaction, where HF is kept rigid, is calculated using the supermolecular unrestricted fourth-order Moller–Plesset perturbation theory. The basis set superposition error corrected potential indicates two minima. The global minimum occurs for the bent Li...FH structure at R=1.95 A and θ=70° with a relatively deep well of De=1,706 cm−1 and the secondary minimum is found for the linear Li...HF configuration at R=4.11 A with a well depth ofDe=288 cm−1. A barrier of 177 cm−1 (with respect to the secondary linear minimum) separates these two minima. In this study 27 bound states of the bent Li...FH minimum and eight bound states of the linear Li...HF minimum up to the Li+HF dissociation threshold are calculated. The energy partitioning using the intermolecular perturbation theory scheme shows that the origins of the stability of the structures studied are entirely different. The global minimum is stabilised using the attractive Coulombic interaction and unrestricted Hartree–Fock deformation energy. The latter term originates from the mutual electric polarisation effects. The secondary linear minimum is mostly determined by the anisotropy of the repulsive Heitler–London exchange-penetration and attractive dispersion energies.

On the structure and physical origin of weak interaction between H and CO2

The potential energy surface of the radical H⋯CO2 van der Waals complex, described by Jacobi coordinates (r=1.1755Å,R,Θ), was investigated using the supermolecular coupled cluster treatment. Our calculations corrected for the basis set supperposition error predict global minimum for the perpendicular arrangement (Θ=90°). This minimum was found at R=3.20 Å with a well depth of De=343.1μEh. The second stationary point has a well depth of 173.6μEh at linear orientation for R=4.46Å and corresponds to the saddle point. The physical origin of the studied weak interaction was analysed by the intermolecular perturbation theory based on the single determinant unrestricted Hartree–Fock wave function. The separation of the interaction energy shows that the locations of the indicated structure is primarily determined by delicate balance between the rapid decrease of the repulsive Heitler–London exchange-penetration energy versus attractive Hartree–Fock dispersion components over the carbon atom.

Ab initio Study of the Li-CO van der Waals Complex

The adiabatic potential energy surface (PES) of the Li-CO complex in the van der Waals region, described by Jacobi coordinates (r = 1.15 Å, R, Θ), was investigated using the supermolecular coupled-clusters CCSD(T) method. Our calculations indicate minima for bent arrangements. The first minimum was found on the carbon side of CO molecule at R = 5.27 Å (Θ = 50.7°) with a well depth of De = -167.2 μEh. The second minimum is indicated at R = 5.35 Å (Θ = 148.7°) with a well depth of De = -121.9 μEh. The saddle point is localised at θ = 111.5° and R = 5.35 Å. The physical origin of the weak interaction studied was analysed by the intermolecular perturbation theory based on the single determinant UHF wave function. The separation of the interaction energies shows that the locations of the predicted stable bent structures are primarily determined by the anisotropy of the repulsive Heitler-London exchange penetration and attractive dispersion and induction energy components.

Ab Initio Study of the HF(Χ )−H(2S) van der Waals Complex

The adiabatic potential energy surface (PES) of the HF(X 1 )−H(2S) van der Waals complex, described by Jacobi coordinates (r = 0.918 Å, R, ϑ), was investigated using the supermolecular unrestricted fourth-order Møller−Plesset perturbation theory. Our calculations indicate two minima for the linear arrangements. The primary minimum was found for the H···HF geometry at R = 3.13 Å with a well depth of De = 98.01 cm-1 and the secondary one for the H···FH orientation at R = 3.21 Å with a well depth of De = 31.36 cm-1. The presented PES reveals that these minima are separated by a barrier of 81.73 cm-1 (with respect to the primary minimum) at R = 3.17 Å and ϑ = 99°. The physical origin of the studied weak interaction was analyzed by the intermolecular perturbation theory on the basis of the single determinant UHF wave function. The separation of the interaction energy shows that the locations of the predicted stable structures are primarily determined by the anisotropy of the repulsive Heitler−London exchange−penetration and attractive dispersion + induction energy components. Dynamical calculations have also been performed to determine the bound states of the studied complex. They show that the ground state is 21.01 cm-1 below the dissociation to HF(X 1 ) + H(2S).

Potential energy surface and infrared spectrum of the Ar–H2Cl+ ionic complex

The infrared photodissociation spectrum of the Ar–H2Cl+ dimer has been recorded in the vicinity of the Cl–H stretch fundamentals of bare H2Cl+. Eleven Q branches of a strong perpendicular transition of a (near) prolate symmetric top are observed. The position and rotational structure of the band are consistent with an assignment to the free Cl–H stretch fundamental of a proton-bound Ar–HClH+ dimer. The global minimum on the intermolecular potential energy surface of Ar–H2Cl+, calculated at the MP2/aug-cc-pVTZ# level of theory, corresponds to the proton-bound structure with an intermolecular separation of Re=1.97 Å and a well depth of De=1860 cm−1. The slightly nonlinear ionic hydrogen bond is directional with large barriers (Vb) for internal rotation of H2Cl+ via planar transition states with C2v symmetry: Vb∼750 and 1330 cm−1 for the bridged (Re=3.45 Å, De=1107 cm−1) and chlorine-bound (Re=3.38 Å, De=531 cm−1) structures. The molecular constants of the observed transition, ν0=2663.1 cm−1 and A=10.35 cm−1, are in good agreement with the values calculated for the proton-bound equilibrium geometry, ν0=2665.4 cm−1 and Ae=10.28 cm−1.

Ab initio potential energy surface for the Ar(1S)+OH(X2Π) interaction and bound rovibrational states

Adiabatic potential energy surfaces for the A′2 and A″2 states of the Ar(1S)–OH(X2Π) complex were calculated using supermolecular unrestricted fourth-order Møller–Plesset perturbation theory and a large correlation consistent basis set supplemented with bond functions. The potential energy surface (PES) of the A′ state has two minima. The global minimum from the unrestricted coupled-cluster calculations with single, double, and noniterative triple excitations occurs for the collinear geometry Ar–H–O at R=7.08a0 with a well depth of De=141.2 cm−1. There is also a local minimum for the skewed T-shaped form, whereas the Ar–O–H arrangement corresponds to a saddle point. The PES of the A″ state also has two minima, which occur for the two collinear isomers. A variational calculation of the bound rovibrational states was performed. The calculated binding energy, D0=93.8 cm−1, and the energies of the bound vibrational states are in good agreement with experiment [see Berry et al., Chem. Phys. Lett. 178, 301 (1991) and Bonn et al., J. Chem. Phys. 112, 4942 (2000), preceding paper].

Ab initio study of the intermolecular potential surface of He–NH3

The intermolecular potential surface for the van der Waals complex He–NH3 is studied by ab initio calculation using fourth-order Møller–Plesset perturbation theory (MP4) with a bond function basis set. The calculation gives a global minimum at R=3.26 Å, θ=89°, φ=60° (in a Jacobi coordinate system) with a well depth of De=32.96 cm−1, along with barriers of 23.09 and 20.86 cm−1 for in-plane rotations at θ=0° and 180°, respectively, and a barrier of 10.45 cm−1 for out-of-plane rotation at θ=89°, φ=0°. The potential energy surface of He–NH3 is compared to those of Ar–NH3 and He–H2O, respectively.