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Gervais Chapuis

Cette personne a quitté l’EPFL

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Publications associées (39)

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Differential geometry: a natural tool for describing symmetry operations

Gervais Chapuis, Kurt Schenk

Differential geometry provides a useful mathematical framework for describing the fundamental concepts in crystallography. The notions of point and associated vector spaces correspond to those of manifold and tangent space at a given point. A space-group o ...

International Union of Crystallography2009

LiZnNb4O11.5: A novel oxygen deficient compound in the Nb-rich part of the Li2O–ZnO–Nb2O5 system

Gervais Chapuis, Philip Pattison, Alla Arakcheeva

A novel lithium zinc niobium oxide LiZnNb4O11.5 (LZNO) has been found in the Nb-rich part of Li2O–ZnO–Nb2O5 system. LZNO, with an original a-PbO2 related structure, has been synthesized by the routine ceramic technique and characterized by X-ray diffractio ...

2010

The alpha(2)-polymorph of salicylideneaniline

Gervais Chapuis, Philip Pattison

N-Salicylideneaniline (SA), C13H11NO, belongs to the large family of aromatic Schiff bases. It is of particular importance owing to its reversible photoreactivity. SA forms two photochromic polymorphs, both with two non-coplanar benzene rings. In addition, ...

2005

KSm(MoO4)2, an incommensurately modulated and partially disordered scheelite-like structure

Gervais Chapuis, Philip Pattison, Alla Arakcheeva

The incommensurately modulated scheelite-like KSm(MoO4)2 structure has been refined in the monoclinic superspace group I2/b(ab0)00 by the Rietveld method on the basis of synchrotron radiation powder diffraction data. The systematic broadening of satellite ...

2008

SUPERFLIP– a computer program for the solution of crystal structures by charge flipping in arbitrary dimensions

Gervais Chapuis

SUPERFLIP is a computer program that can solve crystal structures from diffraction data using the recently developed charge-flipping algorithm. It can solve periodic structures, incommensurately modulated structures and quasicrystals from X-ray and neutron ...

2007

One-dimensional composite host-guest structure in BaVS3

László Forró, Helmuth Berger, Gervais Chapuis, Philip Pattison, Alla Arakcheeva, Neven Barisic

A detailed synchrotron X-ray diffraction (XRD) study performed with a single crystal of BaVS3 (barium vanadium trisulfide) in the temperature range between 10 and 295 K is reported. Aside from the known tetragonal–orthorhombic (240 K) and orthorhombic–mono ...

2021

The role of second coordination-sphere interactions in incommensurately modulated structures, using beta-K5Yb( MoO4)(4) as an example

Gervais Chapuis, Alla Arakcheeva

The incommensurate palmierite-like structure of beta-K5Yb(MoO4)(4), potassium ytterbium tetramolydate, has been refined in the (3 + 1)- dimensional monoclinic superspace group X2/m(0 rho 0) 00, with X = [0 0 0 0; 1/2 1/2 0 0; 0 0 1/2 1/2; 1/2 1/2 1/2 1/2] ...

2005

Dieter Schwarzenbach (1936-2024)

Gervais Chapuis

Dieter passed away at the hospital in Lausanne, Switzerland, after a long neurodegenerative decline. He leaves behind his wife, Vera, and his two children, Charlotte and Thomas. I met Dieter in 1966 when I started my doctoral studies at the Institute of Cr ...

International Union of Crystallography (IUCr)2024

From space to superspace and back: Superspace Group Finder

Gervais Chapuis, Ivan Orlov

The symmetry of a commensurately modulated crystal structure can be described in two different ways: in terms of a conventional three-dimensional space group or using the superspace concept in (3 + d) dimensions. The three-dimensional space group is obtain ...

2008

Crystal Structure and Optical and Magnetic Properties of Pr2(MoO4)3

Gervais Chapuis, Philip Pattison, Alla Arakcheeva

Praseodymium molybdate Pr2(MoO4)3 was synthesized using the standard ceramic route. The crystal structure of the material has been successfully solved in superspace group I2/b(Rβ0)00 with lattice constants a = 5.30284(4), b = 5.32699(3), c = 11.7935(1)A° , ...

2010

Validating the model of a (3+1)-dimensional incommensurately modulated structure as generator of a family of compounds for the Eu2(MoO4)3 scheelite structure

Gervais Chapuis, Philip Pattison, Alla Arakcheeva

The previously proposed model postulating that the incommensurately modulated KNd(MoO

_4

)

_2

structure can act as a generator of the scheelite family members is validated here by refining the crystal structure of europium molybdate, Eu

_2

(MoO

_4

)

_3

. ...

2009

Atomic clusters and phase transitions in the metastable beta-Ta phase between 4.2 and 293 K

Gervais Chapuis, Alla Arakcheeva

Atomic clusters were identified in the ground state of the non-equilibrium Ta phase (Frank-Kasper sigma-structure type) at 15, 120 and 293K. The evolution of the clusters with temperature leads to two phase transformations at 65 and 150K which are related ...

IOP Publishing - EPL Association2005

Prof. François Rothen 17.3.1936 - 17.2.2023

Gervais Chapuis

2023

Application of micro X-ray diffraction to investigate the reaction products formed by the alkali–silica reaction in concrete structures

Gervais Chapuis, Philip Pattison, Alla Arakcheeva

Alkali-silica reaction (ASR) is one of the most important deterioration mechanisms in concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was employed to characterize the mineral phases for ...

Pergamon-Elsevier Science Ltd2016

Incommensurate phases

Gervais Chapuis

Incommensurately modulated crystalline phases are part of a more general family called aperiodic crystals. Their symmetry is treated within the theoretical framework of superspace groups that is a generalization of the 3D space groups that are used for con ...

Academic Press2024

Producing highly complicated materials. Nature does it better

Gervais Chapuis

Through the years, mineralogical studies have produced a tremendous amount of data on the atomic arrangement and mineral properties. Quite often, structural analysis has led to elucidate the role played by minor components, giving interesting insights into ...

2020

Space groups and their description and transformations of coordinate systems

Gervais Chapuis

Wiley for the International Union of Crystallography2021

The role of silver on the stabilization of the incommensurately modulated structure in calaverite, AuTe2

Gervais Chapuis, Alla Arakcheeva

Structural investigations of several minerals belonging to the calaverite group with composition Au1–xAgxTe2 (x = 0.00, 0.02, 0.05, 0.09, 0.19, and 0.33) indicate that Ag is randomly distributed on the Au sites. This suppresses the valence fluctuation of A ...

Mineralogical Society of America2009

Synthesis, growth and characterization of 4-bromo-4′-nitrobenzylidene aniline (BNBA): a novel nonlinear optical material with a (3+1)-dimensional incommensurately modulated structure

Gervais Chapuis, Philip Pattison, Alla Arakcheeva

The organic nonlinear optical material of 4-bromo-4'-nitrobenzylidene aniline (BNBA, C13H9BrN2O2), a new derivative of benzylideneaniline family, was synthesized and purified by repeated recrystallization. Single crystals of BNBA were grown in acetone solv ...

Royal Society of Chemistry2013

An elementary treatment on the diffraction of crystalline structures

Gervais Chapuis

Although W. L. Bragg's law can be easily derived for beginners in the field of crystallography, its interpretation however seems to cause some difficulties which lies essentially in the relation between the concept of lattice planes and the unit cell const ...

2022