Theoretical study of metal borides stability

We have recently identified metal-sandwich (MS) crystal structures and shown with ab initio calculations that the MS lithium monoboride phases are favored over the known stoichiometric ones under hydrostatic pressure [Phys. Rev. B 73, 180501(R) (2006)]. According to previous studies synthesized lithium monoboride tends to be boron-deficient, however the mechanism leading to this phenomenon is not fully understood. We propose a simple model that explains the experimentally observed off-stoichiometry and show that compared to such boron-deficient phases the MS-LiB compounds still have lower formation enthalpy under high pressures. We also investigate stability of MS phases for a large class of metal borides. Our ab initio results suggest that MS noble metal borides are less unstable than the corresponding AlB$_2$-type phases but not stable enough to form under equilibrium conditions.Comment: 14 pages, 15 figure

Theoretical study of the thermal behavior of free and alumina-supported Fe-C nanoparticles

The thermal behavior of free and alumina-supported iron-carbon nanoparticles is investigated via molecular dynamics simulations, in which the effect of the substrate is treated with a simple Morse potential fitted to ab initio data. We observe that the presence of the substrate raises the melting temperature of medium and large $Fe_{1-x}C_x$ nanoparticles ($x$ = 0-0.16, $N$ = 80-1000, non- magic numbers) by 40-60 K; it also plays an important role in defining the ground state of smaller Fe nanoparticles ($N$ = 50-80). The main focus of our study is the investigation of Fe-C phase diagrams as a function of the nanoparticle size. We find that as the cluster size decreases in the 1.1-1.6-nm-diameter range the eutectic point shifts significantly not only toward lower temperatures, as expected from the Gibbs-Thomson law, but also toward lower concentrations of C. The strong dependence of the maximum C solubility on the Fe-C cluster size may have important implications for the catalytic growth of carbon nanotubes by chemical vapor deposition.Comment: 13 pages, 11 figures, higher quality figures can be seen in article 9 at http://alpha.mems.duke.edu/wahyu

Assessment techniques, database design and software facilities for thermodynamics and diffusion

The purpose of this article is to give a set of recommendations to producers of assessed thermodynamic data, who may be involved in either the critical evaluation of limited chemical systems or the creation and dissemination of larger thermodynamic databases. Also, it is hoped that reviewers and editors of scientific publications in this field will find some of the information useful. Good practice in the assessment process is essential, particularly as datasets from many different sources may be combined together into a single database. With this in mind, we highlight some problems that can arise during the assessment process and we propose a quality assurance procedure. It is worth mentioning at this point, that the provision of reliable assessed thermodynamic data relies heavily on the availability of high quality experimental information. The different software packages for thermodynamics and diffusion are described here only briefly

Compilation and critical analysis of thermodynamic data for ternary alloy systems

The thermodynamic approach in resolving industrial problems concerned with high temperature has led, in the two last decades, to a notable development of both theoretical and experimental studies on multicomponent system. Phase diagram determinations of metallic systems are still carried out very extensively because of their importance in the field of material science, mainly in steelmaking, non-ferrous metallurgy, crystal growth, electroslag- refining, nuclear materials, etc..

CONTRIBUTI PER LA FAMIGLIA DI OREFICI CAENAZZO DA KORČULA

Autor članka na osnovi zlatarskih žigova i povijesnih vrela cijeli niz predmeta iz nadžupske crkve sv. Vlaha u Velikom Stonu, pripisuje stonsko-korčulanskom zlataru Vicenzu Caenazzu, koji djeluje polovinom devetnaestog stoljeća, nastavljajući bogatu lokalnu zlatarsku tradiciju. Razglaba se i manifestacija provincijalizma u neostilskim kretanjima, kao i nestajanje lokalnih radionica pred nabujalom rijekom masovnih proizvoda iz bečkih i tršćanskih radionica.L\u27autore dell\u27articolo, sulla base dei punzoni d\u27oreficeria e delle fonti storiche, attribuisce tutta una serie di oggetti della chiesa sovraparrocchiale di S. Biagio a Veliki Ston all\u27orefice di Ston-Korčula Vicenzo Caenazzo, che fu attivo verso la metà del XVIII secolo, continuando la ricca tradizione dell\u27oreficeria locale. Si analizza anche la manifestazione di provincialismo rappresentata dai movimenti neostilistici, così come dalla scomparsa delle botteghe locali dinanzi all\u27avanzare impetuoso dei prodotti di massa delle botteghe viennesi e triestine

O nepoznatoj pjesmi o bokeljskom jedrenjaku

Pronalazak pjesme na hrvatskom jeziku o gradnji jedrenjaka „Pirro S“, u vlasništvu brodovlasničkog roda Sbutega iz Prčanja u Boki kotorskoj, potvrdio je još jednom tradiciju hrvatske pučke književnosti, prije svega sastavljanja prigodnica u povodu obilježavanja važnih događaja. Pjesma i pismo koji se obrađuju u ovom radu, po svemu sudeći, djelo su narodnjaka Nikole Ostojića (1803. – 1869.), jednoga od prvaka narodnog preporoda na otoku Korčuli. Pjesma o porinuću jedrenjaka „Pirro S“, sagledana u tradiciji hrvatskoga prigodnog pjesništva XIX. stoljeća, vrijedan je jezični spomen kontinuiteta hrvatske pisane riječi u prijelomnim vremenima hrvatske nacionalne integracije u Dalmaciji, nastavljajući se na tradiciju dubrovačkoga književnog kruga