The p-version finite element method for atomic computations [J. Chem. Phys. 91, 7030 (1989)] has been implemented within the frame of second-order Mo/ller–Plesset theory and used to calculate correlation energies rare-gas atoms from He Rn. calculation proceeds through a sequence levels computation that is systematic hierarchic in nature helps estimate error final values. It possible include virtual orbitals very high angular momentum (lmax=12) even heaviest elements; so accurate results can...

The interaction of individual Al atoms with water molecules has been studied from the point view energy by means ab initio and DFT calculations in order to find pathways for generation HAlOH⋅(H2O)n or AlOH⋅(H2O)n+H. potential surface Al(H2O)n+1 (n=0–3) systems explored local minima relevant saddle points. several tends produce low-lying which (for n=2–3) is “inserted” into relatively compact structures molecules, so typically a ring formed containing an Al⋅OH2 moiety. Isomerization such...

Quantum mechanical tunneling of atoms plays a significant role in many chemical reactions. The crossover temperature between classical and quantum movement is convenient preliminary indication the importance for particular reaction. Here we show, using instanton theory, that possible significantly above this specific forms potential energy surface. We demonstrate effect on an analytic as well system. While protons move asynchronously along Grotthuss chain high-temperature range, onset...

The Hartree–Fock equations for atoms are solved with the p version of finite element method, which differs from traditional method in using high order, hierarchic polynomials as basis functions. Recursion formulas developed analytical evaluation integrals, crucial reducing computation time and maintaining accuracy solution. A computational approach is used where solution at a certain level to start calculation next level. Results presented closed open shell taken various columns periodic...

The first step of the reaction two relatively large Alm clusters (m = 17, 28) with a few water molecules has been studied by electronic structure methods. complexes Alm·(H2O)n (n 1-2) have characterized, and saddle points corresponding to in reaction, namely, formation HAlmOH·(H2O)n-1 systems, located. Al28 cluster is special sense it states, singlet triplet, which are very close energy also quite similar equilibrium structures. preferred adsorption sites determined. We find clear...

The dynamics of the first step reaction small Alm clusters m = {3,13} with up to four water molecules has been studied. stage in reaction, which may ultimately result production H2, is generation a HAlmOH·(H2O)n−1 species, can take place through transition states relay type, play different catalytic roles; namely, they be involved directly Grotthuss-like mechanism by forming bridge, or lower saddle point energy interacting bridge. Rate coefficients have computed inclusion tunneling effects....

We present a study of the structural evolution tantalum cluster anions Tan–, 6 ≤ n 13 using combination trapped ion electron diffraction (TIED) experiments with variety electronic structure methods. A genetic algorithm has been employed to establish set likely structures for each cluster, their geometries and energetics have studied by density functional theory (DFT), random phase approximation, two-component (2C) DFT methods, which include spin–orbit coupling. find octahedral Ta6– Ta8– as...

We introduce a meshless method derived by considering the time variable as spatial without need to extend further conditions solution of linear and non-linear hyperbolic PDEs. The is based on moving least squares method, more precisely in Generalized Finite Difference Method which allows us select well-conditioned stars. Several 2D 3D examples including are shown for both regular irregular node distributions. results compared with explicit GFDM terms errors execution time.

The simulation of seismic wave propagation generally requires dealing with complex tridimensional geometries that are irregular in shape and have non‐uniform properties, features make the application generalized finite difference method this field interesting. This work continues extensive developments by research team focused on two‐dimensional domains. In new contribution, general formulation treatment free surface boundary conditions extended for three‐dimensional case, results obtained...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical study of acetyleneboron and acetylenealuminum isomers: the interactions boron aluminum atoms with acetyleneJesus R. Flores Antonio LargoCite this: J. Phys. Chem. 1992, 96, 7, 3015–3021Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April 1992https://pubs.acs.org/doi/10.1021/j100186a044https://doi.org/10.1021/j100186a044research-articleACS PublicationsRequest reuse...

We have updated the chemical model of IRC+10216 developed by Millar, Herbst & Bettens to include recent routes formation sulphuretted hydrocarbons. The are based on a quantum study S+C2H system. In addition, we altered parent species for sulphur reflect new observational results. find that calculations give excellent agreement with observed column densities, and discuss significance these reactions as yet unobserved dark interstellar clouds.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTheoretical studies of possible processes for the interstellar production phosphorus compounds: reaction phosphorus(1+) with ammoniaA. Largo, J. R. Flores, C. Barrientos, and Jesus M. UgaldeCite this: Phys. Chem. 1991, 95, 1, 170–175Publication Date (Print):January 1991Publication History Published online1 May 2002Published inissue 1 January 1991https://pubs.acs.org/doi/10.1021/j100154a034https://doi.org/10.1021/j100154a034research-articleACS...

Abstract The finite element second‐order Møller–Plesset method has been employed to improve the accuracy of correlation energies symmetry‐adapted electron pairs and provide values for coefficient leading term their asymptotic expansions (AEs). use multigrid procedures in combination with radial extrapolation techniques improvement angular through AE coefficients obtained from Hartree–Fock wave function (K. Jankowski et al., Mol. Phys. 2006, 104, 2213) have lead a considerable over previous...

We have studied the use of asymptotic expansions (AEs) for angular momentum extrapolation (to l --> infinity) atomic second-order Moller-Plesset (MP2) correlation energies symmetry-adapted pairs (SAPs). The AEs been defined in terms partial wave (PW) increments to SAP obtained with finite element MP2 method (FEM-MP2), as well variational perturbation a Slater-type orbital basis. employed obtain from PW is general sense that it can be applied methods other than and, if modified, molecular...

We performed surface hopping simulations of Al + H(2)O collisions by a direct semiempirical method, reproducing the conditions previous beam-gas experiments. observed formation HAlOH species, that dissociates to AlOH H after lifetime about 0.6 ps. This species undergoes nonadiabatic transitions its first excited state and is responsible for chemiluminescence in visible range, while Al-H(2)O complex emits infrared. The computed emission band red-shifted with respect experimental one, because...

The dynamics of the oxidation micro-hydrated Al atoms has been studied taking into account effect tunneling. Neutral aggregates type Al·(H2O)n, n = {1–8} and Al·(H2O)n·m(H2O) have considered, where Al·(H2O)n treated by density functional theory (DFT) other m {52, 56} waters represented an effective fragment potential (EFP). results indicate that may take place quite fast a relay-type mechanism occurring within ring water molecules which involves atom, in H atom is transferred. inclusion to...

A p-version FEM-MP2 (finite element Møller-Plesset second order perturbation) program for accurate MP2 correlation energies of closed shell atoms has been further improved: by radial transformations , inclusion global factors the form with a sloping function and discretization in x rather than r. Adding logarithmic extrapolations to sequence obtained from low (linear) finite-element calculations resulted very fast high precision approach energies. The accuracy gain over directly calculated...