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SUMMARY:Synchrotron-based experimental study and theoretical simulation of
  hydrogen desorption for solid-state hydrogen storage material – Mn(BH4)
 2
DTSTART;VALUE=DATE-TIME:20160707T052000Z
DTEND;VALUE=DATE-TIME:20160707T054000Z
DTSTAMP;VALUE=DATE-TIME:20260811T204412Z
UID:indico-contribution-1205@indico.inp.nsk.su
DESCRIPTION:Speakers: Ilia Pankin (Southern Federal University\, IRC "Smar
 t materials")\nThe material under study is manganese borohydride Mn(BH4)2.
  The unique thermodynamics and kinetic properties in combination with high
  volumetric and gravimetric hydrogen densities make this compound a very p
 romising candidate to solid state hydrogen storage. Local atomic structure
  of Mn(BH4)2 upon heating was completely studied by in-situ temperature-de
 pendent measurements of X-ray powder diffraction patterns and Mn K-edge XA
 NES (X-ray Absorption Near Edge Structure) at SNBL-01b beamline of ERSF. D
 iffraction patterns indicate amorphisation during heating the sample above
  110 oC. XANES Mn K-edge spectra also undergo significant changes at the t
 emperature from 120 oC to 160o C. TGA analysis reveals drastic weight redu
 ction (up to 10 mas %) of Mn(BH4)2 at the same temperature range. It was c
 oncluded that temperature induced phase transition which is accompanied by
  sample amorphisation process as well as abundant hydrogen release were ob
 served.\n     We have performed ab-inito structure prediction using pseudo
 potential approaches within DFT approximation (VASP 5.3 code). Structural 
 models with different contents of hydrogen atoms per unit cell were consid
 ered. Cell shape\, cell volume and atomic position were relaxed. The simul
 ation indicates collapse of porous structure and decrease in the interatom
 ic distances Mn-B and Mn-Mn provided by significant reduction of cell volu
 me. To find possible stable structures of dense Mn-B phase we have applied
  evolutionary algorithms as implemented in the USPEX code. Several low-ene
 rgy candidates were selected for further analysis. Owing to amorphisation 
 process we expect that the sample after heating has unhomogeneous structur
 e with a nanodomain features corresponding to various crystalline atomic o
 rdering. XANES Mn K-edge spectra were calculated for the lowest energy str
 uctural models\, predicted by means of simulations. Numerical analysis of 
 the discrepancy between experimental and theoretical XANES spectra was per
 formed in order to verify the MnxBy local structure observed in the experi
 ment.\n\nhttps://indico.inp.nsk.su/event/3/contributions/1205/
LOCATION:Budker INP Conference Hall
URL:https://indico.inp.nsk.su/event/3/contributions/1205/
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