186 research outputs found
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-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 nanoparticles ( = 0-0.16, = 80-1000, non-
magic numbers) by 40-60 K; it also plays an important role in defining the
ground state of smaller Fe nanoparticles ( = 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
The experience of launching a psychological hotline across 21 countries to support Ukrainians in wartime
The current work and further steps of the psychological hotline launched by the National Psychological Association of Ukraine (NPA) are discussed along with a call for action to mental health professionals worldwide. Design/methodology/approach – This paper describes the training and support of the NPA’s hotline staff as well as reflections on the hotline’s work from June 2022 to April 2023. Findings – With broad international support, the NPA’s psychological hotline currently operates in 21 countries providing psychological assistance and referrals to other service providers within Ukraine and abroad. We propose further steps of its work, including international collaboration. Originality/value – Providing citizens of Ukraine with broad public access to evidence-based remote psychological support through NPA’s hotlines is a high priority considering the war’s negative impact on mental health diverse and the limited capacity of the state mental health system. Keywords: crisis interventions, psychological hotline, psychological first aid, Russian invasion, Russian-Ukrainian war, war-related traum
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