The Hunt for Hydrogen in the High-Pressure Phase of Ca(OH)2 and Ca(OD)2: Neutrons Versus X-Rays


Article Preview

A recent measurement on the high-pressure phase of Ca(OH)2 using high-resolution synchrotron X-ray powder diffraction has been carried out on a hydrogenated sample at high-temperature. It complements an earlier time-of-flight neutron measurement carried out in the US on a deuterated sample at low temperature. The two protons are found by Rietveld refinement using a new suitable non-Fourier based strategy, for which GSAS and FullProf yield very similar results. Our X-ray result agrees with the previous neutron study for one proton site only, prompting us to reinvestigate the neutron data. A second new and distinct non Fourier-based strategy coupled with GSAS is used to tackle the latter data and indeed confirms the US results. Whilst the reasons for this X-Ray vs Neutron discrepancy can only be guessed at this stage, the use of the two related proton-finding strategies could be extended beyond our specific study.



Materials Science Forum (Volumes 443-444)

Edited by:

Yvonne Andersson, Eric J. Mittemeijer and Udo Welzel




R. J. Papoular and M. Kunz, "The Hunt for Hydrogen in the High-Pressure Phase of Ca(OH)2 and Ca(OD)2: Neutrons Versus X-Rays", Materials Science Forum, Vols. 443-444, pp. 341-344, 2004

Online since:

January 2004




[1] M. Kunz, K. Leinenweber, J.B. Parise, T. -C. Wu, W.A. Bassett, K. Brister, D.J. Weidner, M.T. Vaughan and Y. Wang: High-Pressure Res. Vol. 14 (1996), p.311.


[2] K. Leinenweber, D.E. Partin, U. Schuelke, M. O'Keefe and R.B. Von Dreele: J. Solid State Chem. Vol. 132 (1997), p.267.

[3] R.J. Papoular: Acta Crystallogr. Vol. A55 supplement (1999), p.127.

[4] M. Catti, G. Ferraris, S. Hull and A. Pavese: Phys. Chem. Minerals, Vol. 22 (1995), p.200.

[5] R.J. Papoular and D.E. Cox: Europhys. Lett., Vol. 32 (1995), p.337.

[6] R.J. Papoular, M. Kunz, A. Freidrich, J. Parise and A. Sani: to be submitted.

[7] P.E. Werner: Z. Kristallog., Vol. 120 (1964), p.375.

[8] P.W. Stephens: J. Appl. Cryst., Vol. 32 (1999), p.281.

[9] W.A. Dollase: J. Appl. Cryst., Vol. 19 (1986), p.267.

[10] J. Rodriguez-Carvajal: FullProf/Wfp2k version 1. 9c (May 2001) , LLB, CEA/Saclay , France.

[11] A.C. Larson and R.B. von Dreele: Los Alamos National Lab, Report LAUR-86-748, USA (2001).

[12] Eric Weinstein's world of Mathematics: http: /www. mathworld. wolfram. com.

[13] CCP14 Website: http: /www. ccp14. ac. uk Look for Tutorials/ CCP14 GSAS based Information.

[14] J. -M. Joubert, R. Cerny, M. Latroche, A. Percheron-Guégan and K. Yvon: J. Appl. Cryst. Vol. 31 (1998), p.327.