title: The dehydrogenation mechanism during the incubation period in nanocrystalline MgH2.
abstract: The dehydrogenation mechanism during the incubation period in nanocrystalline MgH2(low α: converted metal fraction and dα/dt) and the reasons for the occurrence of the incubation period at 320, 350, and 400 °C were investigated. Pre-existing Mg crystallites can enhance Mg nucleation during the incubation period, as suggested by the estimated activation energy for nucleation (12 ± 2 kJ per mol H). The released H-atoms enter MgH2as interstitials, as indicated by the MgH2unit-cell contraction, resulting in increased equatorial Mg-H bond length, decreased charge-density distribution in the interstitial region, as observed from the charge-density maps, and decreased H-H distance in the {001} plane up to the midway of the incubation period. Eventually, hydrogen vacancies are created, as indicated by the red shift in the Egand A1gpeaks of Raman spectra. The high estimated activation energy for the growth of Mg (209 ± 8 kJ per mol H) renders it difficult and explains the reason for the presence of an incubation period.
authors.affiliation: Department of Energy Science & Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India. sankara@iitb.ac.in.
authors.forename: Apurva
authors.initials: A
authors.lastname: Shantilal Gangrade
authors.affiliation: Department of Energy Science & Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India. sankara@iitb.ac.in.
authors.forename: Akhil
authors.initials: A
authors.lastname: Aditya Varma
authors.affiliation: Department of Energy Science & Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India. sankara@iitb.ac.in.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Kishor Gor
authors.affiliation: Department of Energy Science & Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India. sankara@iitb.ac.in.
authors.forename: Sweta
authors.initials: S
authors.lastname: Shriniwasan
authors.affiliation: Department of Energy Science & Engineering, Indian Institute of Technology Bombay, Mumbai-400076, India. sankara@iitb.ac.in.
authors.forename: Sankara Sarma V
authors.identifier: http://orcid.org/0000-0003-1788-1265
authors.initials: SS
authors.lastname: Tatiparti