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2015 年度 実施状況報告書

Simulation of laser-driven many-electron atoms and molecules

研究課題

研究課題/領域番号 15K17805
研究機関東京大学

研究代表者

LOETSTEDT ERIK  東京大学, 理学(系)研究科(研究院), 助教 (80632984)

研究期間 (年度) 2015-04-01 – 2018-03-31
キーワードTDSE / laser-matter interaction / computational chemistry / Hartree-Fock
研究実績の概要

The aim of the present research is to develop an efficient method to solve the time-dependent Schrodinger equation for many-electron atoms and molecules exposed to intense laser pulses. Presently, sophisticated laser systems make it possible to perform very detailed experiments on intense laser-atom and laser-molecule interaction. However, to interpret the experimental results, efficient simulation algorithms are necessary. Standard quantum chemistry software cannot be directly used, since these programs were developed for problems which do not depend on time. Methods that can be used to simulate the real-time motion of electrons in atoms and molecules are crucial to approach the goal of a complete understanding of the correlated motion of laser-driven electrons.
By using the well-established Multi-Configuration Time-Dependent Hartree-Fock (MCTDHF) method as a starting point, I aim to develop a new approximation scheme. In the MCTDHF method, the wave function is written as a sum of time-dependent determinants multiplied with time-dependent CI coefficients. My proposal is to further simplify the wave function by decomposing the array of the CI coefficients into a product form. In this way, much fewer parameters are needed to construct the time-dependent wave function.
During FY2015, I have investigated one particular ansatz for the decomposition of the array of CI coefficients. By applying the method to several model systems, I confirmed the efficiency and usefulness of the method.

現在までの達成度 (区分)
現在までの達成度 (区分)

2: おおむね順調に進展している

理由

During FY2015, I have investigated one particular form of product ansatz for the array of CI coefficients. In the adopted ansatz, the array of CI coefficients is labelled by two indices: one index for the spin-up electrons, and one index for the spin-down electrons. The CI two-index array (a matrix) is then factorized into three matrices of much smaller dimension than the original CI matrix. I call the method the “Factorized CI” method.
The Factorized CI method was implemented and applied to three model systems (a 1D carbon atom, a 1D beryllium atom, and a 1D chain of four hydrogen atoms), where all electrons are restricted to move in one dimension. I confirmed that the results obtained by the Factorized CI method converge to the results obtained by the reference MCTDHF method, provided that a certain expansion length parameter is large enough. A manuscript containing the above results was published in the Journal of Chemical Physics (AIP) in April 2016.
A drawback of the Factorized CI method in its present form is that the spin quantum number is not exactly conserved. A small amount of spin contamination may be present in the wave function. This issue will be addressed in the ensuing two years of the present project.

今後の研究の推進方策

During the present fiscal year (FY2016), I will concentrate my research around two major directions:
1. Development of a more efficient CI matrix factorization scheme. Efforts will be made to find a factorization scheme where the spin quantum number is conserved by construction. Other factorization schemes, where the number of parameters required for the construction of the CI matrix is further reduced, will also be investigated.
2. Implementation of the Factorized CI method for three-dimensional systems. At first, systems with spherical symmetry (atoms) will be investigated. Following a successful demonstration on atomic systems, I will continue with the development of a hybrid grid consisting of a combination of a Cartesian grid and a radial grid. The hybrid grid should allow the treatment of molecular systems with arbitrary symmetry.
I plan to delay the parallelization of the code for supercomputer calculations until the following fiscal year.

備考

Research results are posted on the webpage of the Yamanouchi lab at The University of Tokyo.

  • 研究成果

    (6件)

すべて 2016 2015 その他

すべて 雑誌論文 (1件) (うち査読あり 1件、 謝辞記載あり 1件) 学会発表 (4件) (うち国際学会 2件、 招待講演 1件) 備考 (1件)

  • [雑誌論文] Decomposition of the configuration-interaction coefficients in the multiconfiguration time-dependent Hartree-Fock method2016

    • 著者名/発表者名
      Erik Loetstedt, Tsuyoshi Kato, Kaoru Yamanouchi
    • 雑誌名

      The Journal of Chemical Physics

      巻: 144 ページ: 154111-1~13

    • DOI

      10.1063/1.4947018

    • 査読あり / 謝辞記載あり
  • [学会発表] Efficient solution of the time-dependent Schrodinger equation: Factorized CI approximation in MCTDHF2016

    • 著者名/発表者名
      Erik Loetstedt
    • 学会等名
      ICCMSE 2016, Computational Chemistry Symposium
    • 発表場所
      Athens (Greece)
    • 年月日
      2016-03-17 – 2016-03-20
    • 国際学会 / 招待講演
  • [学会発表] Factorized CI: Simplification of the MCTDHF scheme for laser-driven multi-electron dynamics2015

    • 著者名/発表者名
      Erik Loetstedt
    • 学会等名
      International Symposium on Ultrafast Intense Laser Science 14
    • 発表場所
      Kauai, Hawaii (USA)
    • 年月日
      2015-12-09 – 2015-12-13
    • 国際学会
  • [学会発表] Factorization of time-dependent CI coefficients in MCTDHF2015

    • 著者名/発表者名
      Erik Loetstedt
    • 学会等名
      Annual meeting of the Japan Society for Molecular Science
    • 発表場所
      Tokyo Institute of Technology, Ookayama Campus (Tokyo, Meguro-ku)
    • 年月日
      2015-09-16 – 2015-09-19
  • [学会発表] Factorization of time-dependent CI coefficients in MCTDHF2015

    • 著者名/発表者名
      Erik Loetstedt
    • 学会等名
      12th AMO symposium
    • 発表場所
      The University of Tokyo (Tokyo, Bunkyo-ku)
    • 年月日
      2015-06-19 – 2015-06-20
  • [備考] Webpage of Yamanouchi lab

    • URL

      http://www.yamanouchi-lab.org/e/index.html

URL: 

公開日: 2017-01-06  

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