This is the accepted manuscript made available via CHORUS. The article has been published as: Formation of NaCl-Type Monodeuteride LaD by the Disproportionation Reaction of LaD_{2} A. Machida, M. Honda, T. Hattori, A. Sano-Furukawa, T. Watanuki, Y. Katayama, K. Aoki, K. Komatsu, H. Arima, H. Ohshita, K. Ikeda, K. Suzuya, T. Otomo, M. Tsubota, K. Doi, T. Ichikawa, Y. Kojima, and D. Y. Kim Phys. Rev. Lett. 108, 205501 — Published 14 May 2012 DOI: 10.1103/PhysRevLett.108.205501