title: Hafnium-silicon precipitate structure determination in a new heat-resistant ferritic alloy by precession electron diffraction techniques.
abstract: The structure determination of an HfSi4 precipitate has been carried out by a combination of two precession electron diffraction techniques: high precession angle, 2.2°, single pattern collection at eight different zone axes and low precession angle, 0.5°, serial collection of patterns obtained by increasing tilts of 1°. A three-dimensional reconstruction of the associated reciprocal space shows an orthorhombic unit cell with parameters a = 11.4 Å, b = 11.8 Å, c = 14.6 Å, and an extinction condition of (hkl) h + k odd. The merged intensities from the high angle precession patterns have been symmetry tested for possible space groups (SG) fulfilling this condition and a best symmetrization residual found at 18% for SG 65 Cmmm. Use of the SIR2011 direct methods program allowed solving the structure with a structure residual of 18%. The precipitate objects of this study were reproducibly found in a newly implemented alloy, designed according to molecular orbital theory.
authors.affiliation: Departament de Ciència de Materials i Enginyeria Metal·lúrgica, Facultat de Química, Universitat de Barcelona, C/Martí i Franquès 1-11, Barcelona 08028, Spain.
authors.forename: Désirée
authors.initials: D
authors.lastname: Viladot
authors.affiliation: Centres Cientifics i Tecnològics (CCiT), Universitat de Barcelona/Solé i Sabaris 1-3, Barcelona 08028, Spain.
authors.forename: Joaquim
authors.initials: J
authors.lastname: Portillo
authors.affiliation: Center for Nanotechnology Innovation@NEST, Istituto Italiano di Tecnologia, Pisa 56127, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Gemí
authors.affiliation: NanoMEGAS, Boulevard Edmond Machtens 79, Brussels B-1080, Belgium.
authors.forename: Stavros
authors.initials: S
authors.lastname: Nicolopoulos
authors.affiliation: Departament de Ciència de Materials i Enginyeria Metal·lúrgica, Facultat de Química, Universitat de Barcelona, C/Martí i Franquès 1-11, Barcelona 08028, Spain.
authors.forename: Núria
authors.initials: N
authors.lastname: Llorca-Isern