Publications de Gervais Chapuis

Incommensurate phases

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

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

Prof. François Rothen 17.3.1936 - 17.2.2023

Gervais Chapuis

2023

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

Space groups and their description and transformations of coordinate systems

Gervais Chapuis

Wiley for the International Union of Crystallography2021

One-dimensional composite host-guest structure in BaVS3

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

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

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

Looking deeper into molecular structures with Z' > 1

Gervais Chapuis

2020

Incommensurate atomic density waves in the high-pressure IVb phase of barium

Gervais Chapuis, Alla Arakcheeva, Philip Pattison, Vladimir Dmitriev

The host–guest structures of elements at high pressure discovered a decade ago still leave many open questions due to the lack of precise models based on full exploitation of the diffraction data. This concerns in particular Ba IV, which is stable in the r ...

Int Union Crystallography2017

Aperiodic mineral structures

Gervais Chapuis

2017

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

Gervais Chapuis, Alla Arakcheeva, Philip Pattison

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

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, Alla Arakcheeva, Philip Pattison

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

The luminescence of NaxEu3+(2−x)/3MoO4 scheelites depends on the number of Eu-clusters occurring in their incommensurately modulated structure

Jean-Claude Bünzli, Gervais Chapuis, Alla Arakcheeva, Philip Pattison, Dmitry Logvinovich, Svetlana Eliseeva

Scheelite related compounds with general formula Mn(XO4)m are of interest owing to their optical properties, stability and relatively simple preparation. Eu3+-containing scheelites are considered as red emitting phosphors and the main factors affecting the ...

2012

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

Gervais Chapuis, Alla Arakcheeva, Philip Pattison, Dmitry Logvinovich

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

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

Gervais Chapuis, Alla Arakcheeva, Philip Pattison

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

Differential geometry: a natural tool for describing symmetry operations

Gervais Chapuis, Kurt Schenk, Philippe Kocian

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

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

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, Alla Arakcheeva, Philip Pattison, Jorge Martinez Garcia

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

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

Capabilities and limitations of a (3 + d )-dimensional incommensurately modulated structure as a model for the derivation of an extended family of compounds: example of the scheelite-like structures

Gervais Chapuis, Alla Arakcheeva

2008