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Fundamentale Wachstumsinstabilität für Kristalle welche einer uniaxialen polaren Punktgruppe angehören

English title Fundamental growth instability for molecular crystals nucleating int an uniaxial polar group
Applicant Hulliger Jürg
Number 140309
Funding scheme Project funding (Div. I-III)
Research institution Departement für Chemie und Biochemie Universität Bern
Institution of higher education University of Berne - BE
Main discipline Condensed Matter Physics
Start/End 01.04.2012 - 31.03.2015
Approved amount 423'530.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Physical Chemistry

Keywords (5)

high vacuum deposition; polar crystals; crystal growth; force field calculations; growth instability

Lay Summary (English)

Lead
Lay summary

Can polar molecular crystals really exist? We intend to elaborate a fundamental answer to this question. Growth of molecular crystals nucleating into a polar point group can result in a pronounced anisotropy of the growth speed. Experimental observations have found explanation by the effect of solvents, additives, impurities or genuine building blocks providing kinetic hindrance for attachment sites.

Here a new basic thesis is presented to investigate this phenomenon by (i) vapour growth and (ii) computational methods.

Theoretical work (2000-2001) by the applicant predicts a fundamental growth instability for molecular crystals built from dipolar components near thermodynamic equilibrium: Simulations show a bi-polar state in the sense that along one direction of the polar axis, growth leads to a full reversal of dipoles. It is proposed that the demand for dipole reversal is effecting kinetic hindrance for one direction of the polar axis.

The analysis will involve two steps: (i) High vacuum growth of selected materials suitable for both experimental (determination of growth speed and morphology) and (ii) force field calculations for estimating energy differences responsible for probabilities driving  orientational defect formation. At least three selected molecular examples will be analysed in detail.

In case of agreement of experimental and computational work, this would allow us to answer the initial question: Monopolar pyroelectric (no ferroelectric) molecular crystals can only exist because of a fundamental growth instability leading to kinetic hindrance of one of the two polar growth directions. This would lead to the final conclusion: In principle, a monopolar pyroelectric crystal of this type can not exist.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Orientational disorder: A key to understand polarity of molecular crystals
Hulliger J., Brahimi K., Burgener M., Dulcevscaia G. (2014), Orientational disorder: A key to understand polarity of molecular crystals, in JOURNAL OF MOLECULAR STRUCTURE, 1078, 20-25.
A stochastic principle behind polar properties of condensed molecular matter
Hulliger Jürg, Wüst Thomas, Brahimi Khadidja, Burgener Matthias, Aboulfadl Hanane (2013), A stochastic principle behind polar properties of condensed molecular matter, in New Journal of Chemistry, 37(8), 2229-2235.
Polar vector property of the stationary state of condensed molecular matter
Hulliger Jürg, Cannavacciuolo Luigi, Rech Mathias (2013), Polar vector property of the stationary state of condensed molecular matter, in Symmetry, 6(4), 844-850.
Can mono domain polar molecular crystals exist?
Hulliger Jürg, Wüst Thomas, Brahimi Khadidja, Martínez-García Julio Cesar (2012), Can mono domain polar molecular crystals exist?, in Crystal Growth and Design, 12(11), 5211-5218.

Collaboration

Group / person Country
Types of collaboration
Dr. J. Hauser Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Research Infrastructure
PD Dr. Piero Macchi Universität Bern Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Dr. Michel Bonin Lausanne Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Prof. Dr. Dirk Zahn Germany (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Joint Congress of ACTS-2014 & CGOM11, Nara Japan Talk given at a conference Orientational disorder: a key to understand polarity formation in molecular crystals 17.06.2014 Nara, Japan Hulliger Jürg;
Molecular Simulations of Crystallization from Solution cecam Talk given at a conference What is the stationary real solid state of dipolar molecules? 26.05.2014 Lugano, Switzerland Hulliger Jürg;


Self-organised

Title Date Place
Crystallize Action COST CM1402, Schweizer Koordinator für Programm 01.10.2014 Marseille, France

Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Er züchtet Kristalle im Labor Berner Zeitung German-speaking Switzerland 2012

Associated projects

Number Title Start Funding scheme
101658 Unordnung von Molekülen an Kristallflächen und im Kristallvolumen: Kraftfeldrechnungen 01.10.2003 Project funding (Div. I-III)
129472 Stochastische Polaritätserzeugung in Kristallen und natürlichem Gewebe 01.04.2010 Project funding (Div. I-III)
119800 Hoch Vakuum Abscheidung von polaren Texturen organischer Materialien: Untersuchung pyroelektrischer und dielektrischer Eigenschaften 01.04.2008 Project funding (Div. I-III)
159231 Polaritätsbildung in molekularen Kristallen, natürlichem Gewebe und biomimetischen Materialien 01.04.2015 Project funding (Div. I-III)
159231 Polaritätsbildung in molekularen Kristallen, natürlichem Gewebe und biomimetischen Materialien 01.04.2015 Project funding (Div. I-III)

Abstract

Can polar molecular crystals really exist? We intend to elaborate a fundamental answer to this question. Here a new basic thesis is presented to investigate this phenomenon by (i) vapour growth and (ii) computational methods.Simulations show a bi-polar state in the sense that along one direction of the polar axis, growth leads to a full reversal of dipoles. It is proposed that the demand for dipole reversal is effecting kinetic hindrance for one direction of the polar axis.
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