IJS KOLOKVIJ, petek, 5. junij 2009, prof. Wojciech Grochala

[Andreja Berglez]

Vabim vas na 18. predavanje iz sklopa "Kolokviji na IJS" v letu 2008/09, ki
bo v petek, 5. junija 2009, ob 13:00 uri v Veliki predavalnici Instituta
>Jožef Stefan< na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete
tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke
preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Prof. Wojciech Grochala, 

Faculty of Chemistry, University of Warsaw, Pasteur 1, 02093 Warsaw Poland,

Laboratory of Technology of Novel Functional Materials, Interdisciplinary
Center for Mathematical in

Computational Modelling, University of Warsaw, Pawinskiego 5a, 02106 Warsaw
Poland  

 

 

Iskanje superprevodnosti v spojinah z  dvovalentnim srebrom: 8 let po
napovedi

 

Fluor je med vsemi kemijskimi elementi najbolj elektronegativen. Zato ima
večina binarnih ali višjih anorganskih fluoridov veliko izolatorsko
energijsko vrzel. Poznamo le nekaj kovinskih fluoridov, vendar v teh
primerih fluorove valenčne orbitale le malo prispevajo k elektronskim
transportnim pojavom. V tem prispevku bomo pokazali najnovejše teoretične
izračune TM fluoridov, ki kažejo na možnosti, da bi lahko tvorili nov razred
visokotemperaturnih superprevodnikov. Za to potrebujemo močno mešanje
fluorovih 2p- orbital s kovinskimi valenčnimi funkcijami ter delno
zasedenost pasov. V takem primeru napovedujemo nenavadno močno sklopitev z
mrežnimi nihanji ter potencialno superprevodno stanje pri nizkih
temperaturah. Ti pogoji so izpolnjeni za nenavadne fluoride na osnovi
dvovalentnega srebra -  fluoridoargentati-(II), ki si delijo mnoge lastnosti
z bakrovimi oksidi. Na žalost so v vseh  znanih tovrstnih spojinah
nesparjeni d-elektroni urejeni feromagnetno, v nasprotju z antiferomagnetno
ureditvijo v nedopiranih baker-oksidnih spojinah. Pokazali bomo poskuse
načrtovanja fluoridoargentatov(II)  z antiferomagnetno sklopitvijo.

 

Predavanje bo v angleščini.

Lepo vabljeni!

***

We would like to invite you to 18th lecture of the "Kolokvij na IJS" in the
school year 2008/09. The lecture will be held on Friday, June 5, 2009, at 1
pm at JSI main lecture hall, Jamova 39, Ljubljana. The abstract of the
lecture can be found on website:
<http://www.ijs.si/ijsw/Koledar_prireditev>
http://www.ijs.si/ijsw/Koledar_prireditev, the previous recorded lectures
can be found on website:  <http://videolectures.net/kolokviji_ijs>
http://videolectures.net/kolokviji_ijs. 

********************************************

Prof. Wojciech Grochala, 

Faculty of Chemistry, University of Warsaw, Pasteur 1, 02093 Warsaw Poland

Laboratory of Technology of Novel Functional Materials, Interdisciplinary
Center for Mathematical and

Computational Modelling, University of Warsaw, Pawinskiego 5a, 02106 Warsaw
Poland

 

 

Quest for superconductivity in compounds of divalent silver: 8 years after
the prediction

 

Fluorine is the most electronegative among all chemical bond-forming
elements. Because of this, the vast majority of binary and higher inorganic
fluorides are high-melting large-band gap electronic insulators, which are
transparent in the visible region of the electromagnetic spectrum. Rare
examples of metallic fluorides are known, but valence orbitals of F
marginally participate in the electronic transport in these compounds. In
this account we describe recent theory-driven attempts to turn a family of
TM fluorides into a novel class of high-temperature superconductors.
Substantial mixing of F's 2p orbitals and metal valence functions
('covalence') as well as partial band occupation are needed to generate band
crossing judged responsible for unusually strong vibronic coupling and for
the appearance of superconductivity. This precondition is satisfied for
unusual fluorides of divalent silver - fluoroargentates (II). These
fascinating materials share lots of common features with oxides of Cu(I).
Unfortunately, in all known layered fluorides of silver (II) the unpaired d
electrons of silver order ferromagnetically. This is in contrast to
antiferromagnetic ordering observed for undoped oxocuprates. In this account
attempts will be described of crystal-engineering of fluoroargentates (II)
which target a layered antiferromagnetic precursor of a superconductor.

 

 

We look forward to meeting you at the "Kolokvij na IJS"!

 

 

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