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3. Electronic properties and vibrationally averaged structures of X˜ 2 ∑+ MgOH: a computational molecular spectroscopy study.

Author

Hirano, Tsuneo, Nagashima, Umpei, and Baba, Masaaki

Abstract

For X˜ ²∑+ MgOH, we have calculated the 3D potential energy surface (PES) at the MR-SDCI+Q/[cc-pCV5Z (Mg), aug-cc-pV5Z (O), cc-pV5Z (H)] level and derived the vibrational properties from there using the discrete variable representation (DVR) method. The PES minimum is at the linear structure; hence, MgOH is a ‘‘linear molecule.’’ The 3D PES is shallow, and MgOH tends to bend in the region immediately when either or both Mg-O and O-H bonds become longer than those of the equilibrium structure (re(Mg-O)) 0= 1.7614 Å, (re(O-H))0 = 0.9453 Å, and Le(Mg-O-H) = 180°). The zero-point structure, determined as the expectation values over the DVR3D wavefunctions, has (r(Mg-O)i0 = 1.7837 Å and (r(O-H))0 = 0.9948 Å, and the deviation angle from linearity (r)0 = 26.4º. The harmonic frequencies ωe for the Mg-O stretching, bending, and O-H stretching modes are 768, 142, and 4060 cm-1, respectively, and the corresponding term values v1, v2, and v3 are 752, 156, and 3867 cm-1. All the vibrational behaviors, such as quasi-linear features, unusual relationship v2 > ω2, a large amplitude bending motion, etc., are elucidated in terms of the ab initio electronic wavefunctions and the DVR3D vibrational wavefunctions. We have another piece of evidence to support our postulation that a linear molecule is observed as being bent. [ABSTRACT FROM AUTHOR]

Published
2024
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9. Practical Training in Simple Hückel Theory: Matrix Diagonalization for Highly Symmetric Molecules and Visualization of Molecular Orbitals

Author

Nagaoka, Shin-ichi, Kokubo, Tatsunobu, Teramae, Hiroyuki, and Nagashima?, Umpei

Abstract

At an advanced stage of learning quantum chemistry, undergraduate students usually encounter simple Hückel-molecular-orbital (HMO) theory, whose primitive approach gives very useful insight into the electronic structure of p-conjugated molecules. However, on one hand, computational HMO software, when programmed without using molecular symmetry, does not necessarily output chemically reasonable shapes of degenerate molecular-orbitals in benzene. On the other hand, separately inputting the molecular symmetry into the HMO calculation is mathematically redundant (i.e., duplicate information input). To solve this problem, in this study, a Microsoft Excel macro for obtaining reasonable HMOs of highly symmetric molecules such as benzene was developed. Furthermore, two other Excel macros for readily drawing quantitative contour plots of HMOs were created as student-friendly tools. The practical training in simple HMO theory proposed in the present report using these three macros will be very useful for undergraduate teaching of quantum chemistry in terms of clearly showing the theoretical concept.

Published
2018
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18. A Master-Worker Type Eigensolver for Molecular Orbital Computations

Author

Sakurai, Tetsuya, Kodaki, Yoshihisa, Tadano, Hiroto, Umeda, Hiroaki, Inadomi, Yuichi, Watanabe, Toshio, Nagashima, Umpei, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Kågström, Bo, editor, Elmroth, Erik, editor, Dongarra, Jack, editor, and Waśniewski, Jerzy, editor

Published
2007
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21. A Hybrid Parallel Method for Large Sparse Eigenvalue Problems on a Grid Computing Environment Using Ninf-G/MPI

Author

Sakurai, Tetsuya, Kodaki, Yoshihisa, Umeda, Hiroaki, Inadomi, Yuichi, Watanabe, Toshio, Nagashima, Umpei, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Lirkov, Ivan, editor, Margenov, Svetozar, editor, and Waśniewski, Jerzy, editor

Published
2006
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