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Modeling alkali alanates for hydrogen storage by density-functional band-structure calculations

Published online by Cambridge University Press:  01 December 2005

Ole Martin Løvvik ,
Ole Swang  and
Susanne M. Opalka
Ole Martin Løvvik*
Affiliation:
University of Oslo, Centre for Materials Science and Nanotechnology, 0318 Oslo, Norway
Ole Swang
Affiliation:
SINTEF Materials and Chemistry, N-0314 Oslo, Norway
Susanne M. Opalka
Affiliation:
United Technologies Research Center, East Hartford, Connecticut 06018
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

The alanates (complex aluminohydrides) have relatively high gravimetric hydrogen density and are among the most promising solid-state hydrogen-storage materials. In this work, the crystal structure and electronic structure of pure and mixed-alkali alanates were calculated by ground-state density-functional band-structure calculations. The results are in excellent correspondence with available experimental data. The properties of the pure alanates were compared, and the relatively high stability of the Li3AlH6 phase was pointed out as an important difference that may explain the difficulty of hydrogenating lithium alanate. The alkali alanates are nonmetallic with calculated band gaps around 5 eV and 2.5–3 eV for the tetra- and hexahydrides. The bonding was identified as ionic between the alkali cations and the aluminohydride complexes, while it is polar covalent within the complex. A broad range of hypothetical mixed-alkali alanate compounds was simulated, and four were found to be stable compared to the pure alanates and each other: LiNa2AlH6, K2LiAlH6, K2NaAlH6, and K2.5Na0.5AlH6. No mixed-alkali tetrahydrides were found to be stable, and this was explained by the local coordination within the different compounds. The only alkali alanate that seemed to be close to fulfilling the international hydrogen density targets was NaAlH4.

Keywords

Ab initio calculationElectronic structureEnergy-storage
Type
Articles—Energy and The Environment Special Section
Information
Journal of Materials Research , Volume 20 , Issue 12 , December 2005 , pp. 3199 - 3213
Copyright
Copyright © Materials Research Society 2005

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References

REFERENCES

1.Züttel, A.: Materials for hydrogen storage. Mater. Today 6(9), 24 (2003).CrossRefGoogle Scholar
2.Sandrock, G., Bowman, R.C. Jr.: Gas-based hydride applications: Recent progress and future needs. J. Alloys Compd. 356–357,794 (2003).CrossRefGoogle Scholar
3.Züttel, A.: Hydrogen storage methods. Naturwissenschaften 91, 157 (2003).CrossRefGoogle Scholar
4.Seayad, A.M. and Antonelli, D.M.: Recent advances in hydrogen storage in metal-containing inorganic nanostructures and related materials. Adv. Mater. 16, 765 (2004).CrossRefGoogle Scholar
5.Grochala, P.P.E.W.: Thermal decomposition of the non-interstitial hydrides for the storage and production of hydrogen. Chem. Rev. 104, 1283 (2004).CrossRefGoogle ScholarPubMed
6.Schüth, F., Bogdanovic, B. and Felderhoff, M.: Light metal hydrides and complex hydrides for hydrogen storage. Chem. Commun. 2249 (2004).CrossRefGoogle ScholarPubMed
7.Conte, M., Prosini, P.P. and Passerini, S.: Overview of energy/hydrogen storage: State-of-the-art of the technologies and prospects for nanomaterials. Mater. Sci. Eng. B (in press).Google Scholar
8.Bogdanovic, B. and Schwickardi, M.: Ti-doped alkali metal aluminium hydrides as potential novel reversible hydrogen-storage materials. J. Alloys Compd. 253, 1 (1997).CrossRefGoogle Scholar
9.Jensen, C.M., Zidan, R., Mariels, N., Hee, A. and Hagen, C.: Advanced titanium doping of sodium aluminum hydride: Segue to a practical hydrogen storage material? Int. J. Hydrogen Energy 24, 461 (1999).CrossRefGoogle Scholar
10.Zaluska, A., Zaluski, L. and Ström-Olsen, J.O.: Sodium alanates for reversible hydrogen storage. J. Alloys Compd. 298, 125 (2000).CrossRefGoogle Scholar
11.Gross, K.J., Thomas, G.J. and Jensen, C.M.: Catalyzed alanates for hydrogen storage. J. Alloy Compd. 330–332, 683 (2002).CrossRefGoogle Scholar
12.Meisner, G.P., Tibbetts, G.G., Pinkerton, F.E., Olk, C.H. and Balogh, M.P.: Enhancing low pressure hydrogen storage in sodium alanates. J. Alloys Compd. 337, 254 (2002).CrossRefGoogle Scholar
13.Fichtner, M., Fuhr, O., Kircher, O. and Rothe, J.: Small Ti clusters for catalysis of hydrogen exchange in NaAlH4. Nanotechnol. 14, 778 (2003).CrossRefGoogle Scholar
14.Dymova, T.N., Aleksandrov, D.P., Konoplev, V.N., Silina, T.A. and Sizareva, A.S.: Spontaneous and thermal decomposition of lithium tetrahydridoaluminate LiAlH4: The promoting effect of mechanochemical action on the process. Russ. J. Coord. Chem. 20, 263 (1994).Google Scholar
15.Dymova, T.N., Konoplev, V.N., Aleksandrov, D.P., Sizareva, A.S. and Silina, T.A.: A novel view of the nature of chemical- and phase-composition modifications in lithium hydridoaluminates LiAlH4 and Li3AlH6 on heating. Russ. J. Coord. Chem. 21, 165 (1995).Google Scholar
16.Mal’tseva, N.N., Golovanova, A.I., Dymova, T.N. and Aleksandrov, D.P.: Russ. J. Inorg. Chem. 46, 1793 (2001).Google Scholar
17.Balema, V.P., Dennis, K.W. and Pecharsky, V.K.: Rapid solid-state transformation of tetrahedral [AlH4]− into octahedral [AlH6]3− in lithium aluminohydride. Chem. Commun. 1665 (2000).CrossRefGoogle Scholar
18.Balema, V.P., Wiench, J.W., Dennis, K.W., Pruski, M. and Pecharsky, V.K.: Titanium catalyzed solid-state transformations in LiAlH4 during high-energy ball milling. J. Alloys Compd. 329, 108 (2001).CrossRefGoogle Scholar
19.Chen, J., Kuriyama, N., Xu, Q., Takeshita, H.T. and Sakai, T.: Reversible hydrogen storage via titanium-catalyzed LiAlH4 and Li3AlH6. J. Phys. Chem. B 105, 11214 (2001).CrossRefGoogle Scholar
20.Hauback, B.C., Brinks, H.W. and Fjellvåg, H.: Accurate structure of LiAlD4 studied by combined powder neutron and x-ray diffraction. J. Alloys Compd. 346, 184 (2002).CrossRefGoogle Scholar
21.Brinks, H.W. and Hauback, B.C.: The structure of Li3AlD6. J. Alloys Compd. 354, 143 (2003).CrossRefGoogle Scholar
22.Brinks, H.W., Hauback, B.C., Norby, P. and Fjellvåg, H.: The decomposition of LiAlD4 studied by in-situ x-ray and neutron diffraction. J. Alloys Compd. 351, 222 (2003).CrossRefGoogle Scholar
23.Vajeeston, P., Ravindran, P., Vidya, R., Fjellvåg, H. and Kjekshus, A.: Huge-pressure-induced volume collapse in LiAlH4 and its implications to hydrogen storage. Phys. Rev. B 68, 212101 (2003).CrossRefGoogle Scholar
24.Vajeeston, P., Ravindran, P., Vidya, R., Fjellvåg, H. and Kjekshus, A.: Pressure-induced phase of NaAlH4: A potential candidate for hydrogen storage? Appl. Phys. Lett. 82, 2257 (2003).CrossRefGoogle Scholar
25.Løvvik, O.M.: Periodic band calculation on low index surfaces of crystalline LiAlH4. J. Alloys Compd. 356–357, 178 (2003).CrossRefGoogle Scholar
26.Chung, S-C. and Morioka, H.: Thermochemistry and crystal structures of lithium, sodium and potassium alanates as determined by ab initio simulations. J. Alloys. Compd. 372, 92 (2004).CrossRefGoogle Scholar
27.Blanchard, D., Brinks, H.W., Hauback, B.C. and Norby, P.: Desorption of LiAlH4 with Ti- and V-based additives. Mater. Sci. Eng. B-Solid State Mater. Adv. Technol. 108, 54 (2004).CrossRefGoogle Scholar
28.Vajeeston, P., Ravindran, P., Kjekshus, A. and Fjellvåg, H.: Structural stability and electronic structure for Li3AlH6. Phys. Rev. B 69, 020104 (2004).CrossRefGoogle Scholar
29.Løvvik, O.M., Opalka, S.M., Brinks, H.W. and Hauback, B.C.: Crystal structure and thermodynamic stability of the lithium alanates LiAlH4 and Li3AlH6. Phys. Rev. B 69, 134117 (2004).CrossRefGoogle Scholar
30.Løvvik, O.M.: Adsorption of Ti on LiAlH4 surfaces studied by band-structure calculations. J. Alloys Compd. 373, 28 (2004).CrossRefGoogle Scholar
31.Løvvik, O.M. and Swang, O.: Structure and stability of possible new alanates. Europhys. Lett. 607, 607 (2004).CrossRefGoogle Scholar
32.Løvvik, O.M. and Swang, O.: Crystal structures and electronic structures of alkali aluminohexahydrides from density-functional calculations. J. Alloys Compd. (in press).Google Scholar
33.Kang, J.K., Lee, J.Y., Muller, R.P. and Goddard, W.A.: Hydrogen storage in LiAlH4: Predictions of the crystal structures and reaction mechanisms of intermediate phases from quantum mechanics. J. Chem. Phys. 121, 10623 (2004).CrossRefGoogle ScholarPubMed
34.Andrei, C.M., Walmsley, J.C., Brinks, H.W., Holmestad, R., Srinivasan, S.S., Jensen, C.M. and Hauback, B.C.: Electron microscopy studies of lithium aluminium hydrides. J. Alloys Compd. (in press).Google Scholar
35.Brinks, H.W., Fossdal, A., Fonneløp, J.E. and Hauback, B.C.: Crystal structure and stability of LiAlH4 with TiF3 additive. J. Alloys Compd. (in press).Google Scholar
36.Balema, V.P., Pecharsky, V.K. and Dennis, K.W.: Solid-state phase transformations in LiAlH4 during high-energy ball milling. J. Alloys Compd. 313, 69 (2000).CrossRefGoogle Scholar
37.Zidan, R.A., Takara, S., Hee, A.G. and Jensen, C.M.: Hydrogen cycling behavior of zirconium and titanium-zirconium-doped sodium aluminum hydride. J. Alloys Compd. 285, 119 (1999).CrossRefGoogle Scholar
38.Bogdanovic, B., Brand, R.A., Marjanovic, A., Schwickardi, M. and Tolle, J.: Metal-doped sodium aluminium hydrides as potential new hydrogen-storage materials. J. Alloys Compd. 302, 36 (2000).CrossRefGoogle Scholar
39.Gross, K.J., Guthrie, S., Takara, S. and Thomas, G.J.: In-situ x-ray diffraction study of the decomposition of NaAlH4. J. Alloys Compd. 297, 270 (2000).CrossRefGoogle Scholar
40.Zaluska, A., Zaluski, L. and Ström-Olsen, J.O.: Structure, catalysis and atomic reactions on the atomic scale: A systematic approach to metal hydrides for hydrogen storage. Appl. Phys. A 72, 157 (2001).CrossRefGoogle Scholar
41.Jensen, C.M. and Gross, K.J.: Development of catalytically enhanced sodium aluminum hydride as a hydrogen-storage material. Appl. Phys. A 72, 213 (2001).CrossRefGoogle Scholar
42.Bogdanovic, B. and Schwickardi, M.: Ti-doped NaAlH4 as a hydrogen-storage material–preparation by Ti-catalyzed hydrogenation of aluminum powder in conjunction with sodium hydride. Appl. Phys. A 72, 221 (2001).CrossRefGoogle Scholar
43.Thomas, G.J., Gross, K.J., Yang, N.Y.C. and Jensen, C.M.: Microstructural characterization of catalyzed NaAlH4. J. Alloys Compd. 330–332, 702 (2002).CrossRefGoogle Scholar
44.Sandrock, G., Gross, K.J., Jensen, G.J.T.C., Meeker, D. and Takara, S.: Engineering considerations in the use of catalyzed sodium alanates for hydrogen storage. J. Alloys Compd. 330–332, 696 (2002).CrossRefGoogle Scholar
45.Sun, D., Kiyobayashi, T., Takeshita, H.T., Kuriyama, N. and Jensen, C.M.: X-ray diffraction studies of titanium and zirconium doped NaAlH4: Elucidation of doping induced structural changes and their relationship to enhanced hydrogen storage properties. J. Alloys Compd. 337, L8 (2002).CrossRefGoogle Scholar
46.Gross, K.J., Sandrock, G. and Thomas, G.J.: Dynamic in-situ x-ray diffraction of catalyzed alanates. J. Alloys Compd. 330–332, 691 (2002).CrossRefGoogle Scholar
47.Anton, D.L.: Hydrogen desorption kinetics in transition metal modified NaAlH4. J. Alloys Compd. 356–357, 400 (2003).CrossRefGoogle Scholar
48.Gross, K.J., Majzoub, E.H. and Spangler, S.W.: The effects of titanium precursors on hydriding properties of alanates. J. Alloys Compd. 356–357, 423 (2003).CrossRefGoogle Scholar
49.Balogh, M.P., Tibbetts, G.G., Pinkerton, F.E., Meisner, G.P. and Olk, C.H.: Phase changes and hyrogen release during decomposition of sodium alanates. J. Alloys Compd. 350, 136 (2003).CrossRefGoogle Scholar
50.Kiyobayashi, T., Srinivasan, S.S., Sun, D. and Jensen, C.M.: Kinetic study and determination of the enthalpies of activation of the dehydrogenation of titanium- and zirconium-doped NaAlH4 and Na3AlH6. J. Phys. Chem. A 107, 7671 (2003).CrossRefGoogle Scholar
51.Sun, D., Srinivasan, S.S., Kiyobayashi, T., Kuriyama, N. and Jensen, C.M.: Rehydrogenation of dehydrogenated NaAlH4 at low temperature and pressure. J. Phys. Chem. B 107, 10176 (2003).CrossRefGoogle Scholar
52.Bogdanovic, B., Felderhoff, M., Germann, M., Härtel, M., Pommerin, A., Schüth, F., Weidenthaler, C. and Zibrowius, B.: Investigation of hydrogen discharging and recharging processes of Ti-doped NaAlH4 by x-ray diffraction analysis (XRD) and solid-state NMR spectroscopy. J. Alloys Compd. 350, 246 (2003).CrossRefGoogle Scholar
53.Bogdanovic, B., Felderhoff, M., Kaskel, S., Pommerin, A., Schlichte, K. and Schüth, F.: Improved hydrogen storage properties of Ti-doped sodium alanate using titanium nanoparticles as doping agents. Adv. Mater. 15, 1012 (2003).CrossRefGoogle Scholar
54.Majzoub, E.H. and Gross, K.J.: Titanium-halide catalyst-precursors in sodium aluminum hydrides. J. Alloys Compd. 356–357, 363 (2003).CrossRefGoogle Scholar
55.Weidenthaler, C., Pommerin, A., Felderhoff, M., Bogdanovic, B. and Schüth, F.: On the state of the titanium and zirconium in Ti- or Zr-doped NaAlH4 hydrogen storage material. Phys. Chem. Chem. Phys. 5, 5149 (2003).CrossRefGoogle Scholar
56.Fichtner, M., Engel, J., Fuhr, O., Kircher, O. and Rubner, O.: Nanocrystalline aluminium hydrides for hydrogen storage. Mater. Sci. Eng. B 108, 42 (2004).CrossRefGoogle Scholar
57.Kircher, O. and Fichtner, M.: Hydrogen exchange kinetics in NaAlH4 catalyzed in different decomposition states. J. Appl. Phys. 95, 7748 (2004).CrossRefGoogle Scholar
58.Srinivasan, S.S., Brinks, H.W., Hauback, B.C., Sun, D. and Jensen, C.M.: Long term cycling behavior of titanium doped NaAlH4 prepared through solvent mediated milling of NaH and Al with titanium dopant precursors. J. Alloys Compd. 377, 283 (2004).CrossRefGoogle Scholar
59.Luo, W. and Gross, K.J.: A kinetics model of hydrogen absorption and desorption in Ti-doped NaAlH4. J. Alloys Compd. 385, 224 (2004).CrossRefGoogle Scholar
60.Léon, A., Kircher, O., Rothe, J. and Fichtner, M.: Chemical state and local structure around titanium atoms in NaAlH4 doped with TiCl3 using x-ray absorption spectroscopy. J. Phys. Chem. B 108, 16372 (2004).CrossRefGoogle Scholar
61.Ozolins, V., Majzoub, E.H. and Udovic, T.J.: Electronic structure and Rietveld refinement parameters of Ti-doped sodium alanates. J. Alloys Compd. 375, 1 (2004).CrossRefGoogle Scholar
62.Felderhoff, M., Klementiev, K., Grünert, W., Spliethoff, B., Tesche, B., von Colbe, J.M.B., Bogdanovic, B., Härtel, M., Pommerin, A., Schüth, F. and Weidenthaler, C.: Combined TEM-EDX and XAFS studies of Ti-doped sodium alanate. Phys. Chem. Chem. Phys. 6, 4369 (2004).CrossRefGoogle Scholar
63.Brinks, H.W., Jensen, C.M., Srinivasan, S.S., Hauback, B.C., Blanchard, D. and Murphy, K.: Synchrotron x-ray and neutron diffraction studies of NaAlH4 containing Ti additives. J. Alloys Compd. 376, 215 (2004).CrossRefGoogle Scholar
64.Sun, D., Srinivasan, S.S., Chen, G. and Jensen, C.M.: Rehydrogenation and cycling studies of dehydrogenated NaAlH4. J. Alloys Compd. 373, 265 (2004).CrossRefGoogle Scholar
65.Walters, R.T. and Scogin, J.H.: A reversible hydrogen storage mechanism for sodium alanate: The role of alanes and the catalytic effect of the dopant. J. Alloys Compd. 379, 135 (2004).CrossRefGoogle Scholar
66.Wang, P. and Jensen, C.M.: Method for preparing Ti-doped NaAlH4 using Ti powder: Observation of an unusual reversible dehydrogenation behavior. J. Alloys Compd. 379, 99 (2004).CrossRefGoogle Scholar
67.Wang, P. and Jensen, C.M.: Preparation of Ti-doped sodium aluminum hydride from mechanical milling of NaH/Al with off-the-shelf Ti powder. J. Phys. Chem. B 108, 15827 (2004).CrossRefGoogle Scholar
68.Graetz, J., Reilly, J.J., Johnson, J., Ignatov, A.Y. and Tyson, T.Y.: X-ray absorption study of Ti-activated sodium aluminum hydride. Appl. Phys. Lett. 85, 500 (2004).CrossRefGoogle Scholar
69.Iniguez, J., Yildirim, T., Udovic, T.J., Sulic, M. and Jensen, C.M.: Structure and hydrogen dynamics of pure and Ti-doped sodium alanate. Phys. Rev. B 70, 060101 (2004).CrossRefGoogle Scholar
70.Løvvik, O.M. and Opalka, S.M.: Density-functional calculations of Ti-enhanced NaAlH4. Phys. Rev. B 71, 054103 (2005).CrossRefGoogle Scholar
71.Wang, J., Ebner, A.D., Prozorov, T., Zidan, R. and Ritter, J.A.: Effect of graphite as co-dopant on the dehydrogenation and hydrogenation kinetics of Ti-doped sodium aluminum hydride. J. Alloys Compd. (in press).Google Scholar
72.Wang, J., Ebner, A.D., Zidan, R. and Ritter, J.A.: Synergistic effects of co-dopants on the dehydrogenation kinetics of sodium aluminum hydride. J. Alloys Compd. 391, 245 (2005).CrossRefGoogle Scholar
73.Gomes, S., Renaudin, G., Hagemann, H., Yvon, K., Sulic, M.P. and Jensen, C.M.: Effects of milling, doping and cycling of NaAlH4 studied by vibrational spectroscopy and x-ray diffraction. J. Alloys Compd 390, 305 (2005).CrossRefGoogle Scholar
74.Haiduc, A.G., Stil, H.A., Schwarz, M.A., Paulus, P. and Geerlings, J.J.C.: On the fate of the Ti catalyst during hydrogen cycling of sodium alanate. J. Alloys Compd. 393, 252 (2005).CrossRefGoogle Scholar
75.Majzoub, E.H., Herberg, J.L., Stumpf, R., Spangler, S. and Maxwell, R.S.: XRD and NMR investigation of Ti-compound formation in solution-doping of sodium aluminum hydrides: Solubility of Ti in NaAlH4 crystals grown in THF. J. Alloys Compd. (in press).Google Scholar
76.Resana, M., Hamptona, M.D., Lomnessa, J.K. and Slattery, D.K.: Effect of TixAly catalysts on hydrogen storage properties of LiAlH4 and NaAlH4. Int. J. Hydrogen Energy (in press).Google Scholar
77.Andrei, C.M., Walmsley, J.C., Brinks, H.W., Holmestad, R., Srinivasan, S.S., Jensen, C.M. and Hauback, B.C.: Electron-microscopy studies of NaAlH4 with TiF3 additive: Hydrogen-cycling effects. Appl. Phys. A 80, 709 (2005).CrossRefGoogle Scholar
78.Opalka, S.M. and Anton, D.L.: First principles study of sodium-aluminum-hydrogen phases. J. Alloys Comp. 356–357, 486 (2003).CrossRefGoogle Scholar
79.Aguayo, A. and Singh, D.J.: Electronic structure of the complex hydride NaAlH4. Phys. Rev. B 69, 155103 (2004).CrossRefGoogle Scholar
80.Ross, D.J., Halls, M.D., Nazro, A.G. and Aroca, R.F.: Raman scattering of complex sodium aluminimum hydride for hydogen storage. Chem. Phys. Lett. 388, 430 (2004).CrossRefGoogle Scholar
81.de Dompablo, M.E. Arroyo y and Ceder, G.: First principles investigations of complex hydrides AMH4 and A3MH6 (A = Li, Na, K, M=B, Al, Ga) as hydrogen storage systems. J. Alloys Compd. 364, 6 (2004).CrossRefGoogle Scholar
82.Peles, A., Alford, J.A., Ma, Z., Yang, L. and Chou, M.Y.: First-principles study of NaAlH4 and Na3AlH6 complex hydrides. Phys. Rev. B 70, 165105 (2004).CrossRefGoogle Scholar
83.Ke, X. and Tanaka, I.: Decomposition reactions for NaAlH4, Na3AlH6, and NaH: First-principles study. Phys. Rev. B 71, 024117 (2005).CrossRefGoogle Scholar
84.Majzoub, E.H., McCarty, K.F. and Ozolins, V.: Lattice dynamics of NaAlH4 from high-temperature single-crystal Raman scattering and ab initio calculations: Evidence of highly stable AlH4− anions. Phys. Rev. B 71, 024118 (2005).CrossRefGoogle Scholar
85.Hedin, L.: New method for calculating 1-particle Greens function with application to electron-gas problem. Phys. Rev. 139, A796 (1965).CrossRefGoogle Scholar
86.Hybertsen, M.S. and Louie, S.G.: Electron correlation in semiconductors and insulators: Band-gaps and quasi-particle energies. Phys. Rev. B 34, 5390 (1986).CrossRefGoogle Scholar
87.Bastide, J.P., Bonnetot, B., Letoffe, J-M. and Claudy, P.: Polymorphic transition of the trisodium hexahydroaluminate Na3AlH6. Mater. Res. Bull. 16, 91 (1981).CrossRefGoogle Scholar
88.Morioka, H., Kakizaki, K., Chung, S.C. and Yamada, A.: Reversible hydrogen decomposition of KAlH4. J. Alloys Compd. 353, 310 (2003).CrossRefGoogle Scholar
89.Hauback, B.C., Brinks, H.W., Heyn, R.H., Blom, R. and Fjellvåg, H.: The crystal structure of KAlD4. J. Alloys Comps. (in press).Google Scholar
90.Vajeeston, P., Ravindran, P., Kjekshus, A. and Fjellvåg, H.: Crystal structure of KAlH4 from first principle calculations. J. Alloys Compd. 363, L7 (2004).CrossRefGoogle Scholar
91.Claudy, P., Bonnetot, B., Bastide, J-P. and Létoffé, J-M.: Reactions of lithium and sodium aluminium hydride with sodium or lithium hydride. Preparation of a new alumino-hydrode of lithium and sodium LiNa2AlH6. Mater. Res. Bull. 17, 1499 (1982).CrossRefGoogle Scholar
92.Zaluski, L., Zaluska, A. and Ström-Olsen, J.O.: Hydrogenation properties of complex alkali metal hydrides fabricated by mechano-chemical synthesis. J. Alloys Compd. 290, 71 (1999).CrossRefGoogle Scholar
93.Huot, J., Boily, S., Guther, V. and Schulz, R.: Synthesis of Na3AlH6 and Na2LiAlH6 by mechanical alloying. J. Alloys Compd. 283, 304 (1999).CrossRefGoogle Scholar
94.Opalka, S. M., P. Saxe, , and Løvvik, O. M.: Phonon calculations on the mixed-alkali phase LiNa2AlH6. (unpublished).Google Scholar
95.Brinks, H.W. (private communication).Google Scholar
96.Genma, R., Uchida, H.H., Okada, N. and Nishi, Y.: Hydrogen reactivity of Li-containing hydrogen-storage materials. J. Alloys Compd. 356, 358 (2003).CrossRefGoogle Scholar
97.Okada, N., Genma, R., Nishi, Y. and Uchida, H.H.: RE-oxide doped alkaline hydrogen-storage materials prepared by mechanical activation. J. Mater. Sci. 39, 5503 (2004).CrossRefGoogle Scholar
98.Graetz, J., Lee, Y., Reilly, J. J., Park, S., and Vogt, T.: Structure and thermodynamics of the mixed alkali alanates. (unpublished).Google Scholar
99.Bastide, J.P., Claudy, P., Letoffe, J.M. and Hajri, J. El: Preparation and characterization of KAlH4. Rev. Chim. Miner. 24, 248 (1987).Google Scholar
100.Kresse, G. and Hafner, J.: Ab initio molecular-dynamics for liquid-metals. Phys. Rev. B 47, R558 (1993).CrossRefGoogle ScholarPubMed
101.Kresse, G. and Furthmüller, J.: Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169 (1996).CrossRefGoogle ScholarPubMed
102.Kresse, G. and Joubert, D.: From ultrasoft pseudopotentials to the projector augmented-wave method. Phys. Rev. B 59, 1758 (1999).CrossRefGoogle Scholar
103.Perdew, J.P., Chevary, J.A., Vosko, S.H., Jackson, K.A., Pederson, M.R., Singh, D.J. and Fiolhais, C.: Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46, 6671 (1992).CrossRefGoogle ScholarPubMed
104.te Velde, G. and Baerends, E.J.: Precise density-functional method for periodic structures. Phys. Rev. B 44, 7888 (1991).CrossRefGoogle Scholar
105.te Velde, G. and Baerends, E.J.: Numerical integration of polyatomic systems. J. Comput. Phys. 99, 84 (1992).CrossRefGoogle Scholar
106.Rönnebro, E., Noreus, D., Kadir, K., Reiser, A. and Bogdanovic, B.: Investigation of the perovskite related structures of NaMgH3, NaMgF, and Na3AlH6. J. Alloys Compd. 299, 101 (2000).CrossRefGoogle Scholar
107.Hauback, B.C., Brinks, H.W., Jensen, C.M., Murphy, K. and Maeland, A.J.: Neutron diffraction structure determination of NaAlD4. J. Alloys Compd. 358, 142 (2003).CrossRefGoogle Scholar
108.Shannon, R.D.: Revised effective ionic-radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr. A 32, 751 (1976).CrossRefGoogle Scholar
109. WebElements Periodic table. http://www.webelements.com.Google Scholar
110.Silvi, B. and Savin, A.: Classification of chemical-bonds based on topological analysis of electron localization functions. Nature 371, 683 (1994).CrossRefGoogle Scholar
111.Løvvik, O.M.: Predicted crystal structure of calcium alanate Ca(AlH4)2 from density-functional band-structure calculations. Phys. Rev. B (in press).Google Scholar
112. International energy agency hydrogen program, task 17. http://www.ieahia.org/tasks/task17.html.Google Scholar
113. The United States Department of Energy Freedom CAR targets. http://www.hydrogen.energy.gov/.Google Scholar