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Computational Modeling and Characterization of Amorphous Materials

Igram, Dale J
http://orcid.org/0000-0003-4450-1483
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1564347980986716

Abstract Details

2019, Doctor of Philosophy (PhD), Ohio University, Physics and Astronomy (Arts and Sciences).
Two different materials, a non-glass former (a-Si) and a glass former (Ag0.2(Ge35Se65 0.8), were considered for investigation. New structural models of these systems were obtained using state of the art methods. Several physical, electrical, and dynamical attributes of these materials were computed, which revealed atomistic structure, vibrational, electronic and transport properties. To create high-quality continuous random network models of a-Si is difficult using conventional methods. A recently developed algorithm, force-enhanced atomic refinement (FEAR), has shown to provide excellent models. To illustrate this, an investigation was performed with respect to the structural, electronic, and vibrational properties of amorphous silicon, which consisted of several model types of different sizes that were constructed from melt-quench (MQ) and FEAR methods. The results from the FEAR models, as compared to the MQ models, correlated more closely with experiment, even for relatively large structure sizes. In addition, FEAR is generally about a factor of 10 faster than conventional methods. Next, we investigated the static and dynamical properties of a ternary glassy material Ag0.2(Ge35Se65)0.8 using ab initio molecular dynamics (AIMD). The results indicated the host network to be rigid and that additional substructures exist in the model. The radial distribution function of the Ag0.2(Ge35Se65)0.8 model revealed reasonably good agreement with experiment. It has been shown that the model consists of Ge(Se1/2)4 tetrahedra which are quite distorted from ideal. To better comprehend the dynamical properties of this model we performed a detailed analysis of the vibrational modes, which we believe to be a first for such a system. Finally, we examined A1 breathing modes of the corner-sharing tetrahedra where we affirm that these breathing modes are non-local and involve the mixing of modes for different symmetry which results in two bands of A1 breathing modes, thus emphasizing the fact that local molecular vibration modes is an oversimplified approximation for amorphous materials.
David Drabold (Advisor)
David Ingram (Committee Member)
Gang Chen (Committee Member)
Horacio Castillo (Committee Member)
R Damian Nance (Committee Member)
73 p.
Condensed Matter Physics; Theoretical Physics
Molecular dynamics; FEAR; electronic density of states; vibrational analysis; breathing modes

Recommended Citations

Citations

  • Igram, D. J. (2019). Computational Modeling and Characterization of Amorphous Materials [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1564347980986716

    APA Style (7th edition)

  • Igram, Dale. Computational Modeling and Characterization of Amorphous Materials. 2019. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1564347980986716.

    MLA Style (8th edition)

  • Igram, Dale. "Computational Modeling and Characterization of Amorphous Materials." Doctoral dissertation, Ohio University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1564347980986716

    Chicago Manual of Style (17th edition)

ohiou1564347980986716
365
© 2019, all rights reserved.
This open access ETD is published by Ohio University and OhioLINK.