Yuriko Ono

Theoretical study of Ng–NiN2 (Ng=Ar,Ne,He)

It is shown that NiN(2) and noble gas atoms, Ar, Ne, and He, combine with the binding energy of 11.52, 4.06, and 7.37 kcal/mol, respectively, by the multireference perturbational (CASPT2) method. By the density functional theory calculations using MPWPW91 functionals, the Ni-N-N bending frequency in NiN(2) and Ar-NiN(2) is estimated as 310.7 and 358.7 cm(-1), respectively, the latter of which is in good agreement with the corresponding experimental frequency, 357.0 cm(-1), determined for NiN(2) isolated in solid argon.

Theoretical study of Pt-Ng and Ng-Pt-Ng (Ng=Ar,Kr,Xe)

We have investigated the binding of noble-gas (Ng) atoms (Ng=Ar,Kr,Xe) with Pt atom by the ab initio coupled-cluster CCSD(T) method, taking into account the relativistic effects. It is shown that two Ng atoms can bind with Pt atom in linear geometry in the singlet lowest state where the second Ng atom attaches to Pt with the larger binding energy than the first Ng atom. The binding energy is evaluated as 8.2, 17.9, and 33.4 kcal/mol for Ar-Pt-Ar, Kr-Pt-Kr, and Xe-Pt-Xe, respectively, relative to the triplet ground state of the dissociation limit Pt ((3)D)+2Ng. The present results indicate that these Ng-Pt-Ng compounds are possible new gas-phase or matrix species.

Vibrational shifts of HXeCl in matrix environments.

The hybrid quantum-classical simulations are performed to investigate the unusual vibrational spectral shifts of a noble-gas hydride HXeCl in matrix environments (in Ne, Ar, Kr, and Xe matrixes). The high-level ab initio calculations at the CCSD(T) level are employed to construct interaction potential energy surfaces between HXeCl and noble-gas atoms (Ne, Ar, Kr, and Xe). The configurations of noble-gas atoms are sampled by the Monte Carlo simulations and the vibrational levels of HXeCl in the presence of the surrounding noble-gas atoms are solved by the DVR approach. It is found that the H-Xe stretching frequencies are blue-shifted from the isolated gas-phase value in all matrix environments and that the relative blue shifts are in good agreement with the experimental results (Ne < Xe < Kr), demonstrating that the explicit treatment of matrix environments around HXeCl is essential to reproduce the observed unusual vibrational shifts.

Competing effects of rare gas atoms in matrix isolation spectroscopy: A case study of vibrational shift of BeO in Xe and Ar matrices

We investigate the vibrational shift of beryllium oxide (BeO) in Xe matrix as well as in Ar matrix environments by mixed quantum-classical simulation and examine the origin of spectral shift in details. BeO is known to form strong chemical complex with single rare gas atom, and it is predicted from the gas phase calculations that vibrational frequencies are blueshifted by 78 cm(-1) and 80 cm(-1) upon formation of XeBeO and ArBeO, respectively. When the effects of other surrounding rare gas atoms are included by Monte Carlo simulations, it is found that the vibrational frequencies are redshifted by 21 cm(-1) and 8 cm(-1) from the isolated XeBeO and ArBeO complexes, respectively. The vibrational shift of XeBeO in Ar matrix is also calculated and compared with experimental data. In all simulations examined in this paper, the calculated vibrational frequency shifts from the isolated BeO molecule are in reasonable agreement with experimental values. The spectral shift due to the rare-gas-complex formation of RgBeO (Rg = Xe or Ar) is not negligible as seen in the previous studies, but it is shown in this paper that the effects of other surrounding rare gas atoms should be carefully taken into account for quantitative description of the spectral shifts and that these two effects are competing in vibrational spectroscopy of BeO in matrix environments.

Implementation and performance of the artificial force induced reaction method in the GRRM17 program

This article reports implementation and performance of the artificial force induced reaction (AFIR) method in the upcoming 2017 version of GRRM program (GRRM17). The AFIR method, which is one of automated reaction path search methods, induces geometrical deformations in a system by pushing or pulling fragments defined in the system by an artificial force. In GRRM17, three different algorithms, that is, multicomponent algorithm (MC‐AFIR), single‐component algorithm (SC‐AFIR), and double‐sphere algorithm (DS‐AFIR), are available, where the MC‐AFIR was the only algorithm which has been available in the previous 2014 version. The MC‐AFIR does automated sampling of reaction pathways between two or more reactant molecules. The SC‐AFIR performs automated generation of global or semiglobal reaction path network. The DS‐AFIR finds a single path between given two structures. Exploration of minimum energy structures within the hypersurface in which two different electronic states degenerate, and an interface with the quantum mechanics/molecular mechanics method, are also described. A code termed SAFIRE will also be available, as a visualization software for complicated reaction path networks.

Analyses of bifurcation of reaction pathways on a global reaction route map: a case study of gold cluster Au5.

A global reaction route map is generated for Au5 by the anharmonic downward distortion following method in which 5 minima and 14 transition states (TSs) are located. Through vibrational analyses in the 3N - 7 (N = 5) dimensional space orthogonal to the intrinsic reaction coordinate (IRC), along all the IRCs, four IRCs are found to have valley-ridge transition (VRT) points on the way where a potential curvature changes its sign from positive to negative in a direction orthogonal to the IRC. The detailed mechanisms of bifurcations related to the VRTs are discussed by surveying a landscape of the global reaction route map, and the connectivity of VRT points and minima is clarified. Branching of the products through bifurcations is confirmed by ab initio molecular dynamics simulations starting from the TSs. A new feature of the reaction pathways, unification, is found and discussed.

Nontotally symmetric trifurcation of an SN2 reaction pathway

A new type of reaction pathway which involves a nontotally symmetric trifurcation was found and investigated for a typical SN2‐type reaction, NC‐ + CH3X → NCCH3 + X‐ (X = F, Cl). A nontotally symmetric valley‐ridge inflection (VRI) point was located along the C3v reaction path. For X = F, the minimum energy path (MEP) starting from the transition state (TS) leads to a second‐order saddle point with C3v symmetry, which connects three product minima of Cs symmetry. For X = Cl, four product minima have been observed, of which three belong to Cs symmetry and one to C3v symmetry. The branching path from the VRI point to the lower symmetry minima was determined by a linear interpolation technique. The branching mechanism is discussed based on the reaction path curvature and net atomic charges, and the possibility of a nonotally symmetric n‐furcation is discussed.

Response to "Comment on 'Analyses of bifurcation of reaction pathways on a global reaction route map: A case study of gold cluster Au5"' [J. Chem. Phys. 143, 177101 (2015)].

The existence of a valley-ridge transition (VRT) point along the intrinsic reaction coordinate does not always indicate the existence of two minima in the product side, but VRT is a sign of bifurcating nature of dynamical trajectories running on the potential energy surface. It is demonstrated by molecular dynamics simulations.

Visualization of the Intrinsic Reaction Coordinate and Global Reaction Route Map by Classical Multidimensional Scaling

A classical multidimensional scaling (CMDS) method is employed to visualize an intrinsic reaction coordinate (IRC) and a global reaction route map consisting of the equilibrium minima and transition state structures connected by the IRC network. As demonstrations, the method was applied to the IRCs of the intramolecular proton transfer in malonaldehyde and the SN2 reaction of OH- + CH3F → CH3OH + F-, which are both well described by two principal coordinates. Next, the method was applied to the global reaction route map of the Au5 cluster; the resulting map shows appropriate positions of five minima and 14 transition states in a reduced 2- or 3-dimensional coordinate space successfully.