293971 A DFT Study of NaMgH3 (001) Surfaces : Lattice Dynamics

Tuesday, April 30, 2013: 2:00 PM
Presidio A (Grand Hyatt San Antonio)
Fernando A. Soto, Louisiana Tech University, Ruston, LA and Daniela S. Mainardi, Chemical engineering, Louisiana Tech University, Ruston, LA

A DFT Study of NaMgH3 (001) Surfaces : Lattice Dynamics

Authors: Fernando Soto1, Daniela S. Mainardi2

1Institute for Micro-manufacturing, Louisiana Tech University

2Institute for Micro-manufacturing, Chemical Engineering, Louisiana Tech University


            Complex metal hydrides have emerged as one of the most promising solid-state hydrogen storage materials[1] due to their high hydrogen volumetric and gravimetric storage capacities. Mg-based alloys such as NaMgH3 are especially interesting because of their light weight[2] and hydrogen mobility[3]. However, a solid state material must meet a set of technical requirements regarding gravimetric and volumetric densities, operating temperature, delivery pressure, fueling time, cycle life, cost and safety that no system currently satisfies[4]. For this reason, efforts have been devoted to decrease the desorption temperature and enhance the kinetics of complex metal hydrides[5]. For instance, thermodynamics and kinetics have been improved by doping NaAlH4 with transition-metals[6] [7]; however, the improvement in dehydrating and hydrating kinetics occurs at the expense of hydrogen content[8]. Thus, the search for optimal storage materials, catalytic additives and destabilization options remains open.

            In spite of considerable experimental and computational work[9-17], a complete understanding of the vibrational properties such as phonons and dispersion of the NaMgH3 (001) surfaces is still lacking. The study of surface phonons provides valuable insight into the surface structure and other phenomena specific to the surface, which can differ from the bulk. A density functional theory study addressing these issues is important in order to achieve a deeper understanding of the relevant mechanisms that could facilitate hydrogen desorption in this material.

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