Free energy of the bcc-liquid interface and the Wulff shape as predicted by the Phase-Field Crystal model

The Euler-Lagrange equation of the phase-field crystal (PFC) model has been solved under appropriate boundary conditions to obtain the equilibrium free energy of the body centered cubic crystal-liquid interface for 18 orientations at various reduced temperatures in the range $\epsilon\in\left[0,0.5\right]$. While the maximum free energy corresponds to the $\left\{ 100\right\}$ orientation for all $\epsilon$ values, the minimum is realized by the $\left\{ 111\right\}$ direction for small $\epsilon\,(<0.13)$, and by the $\left\{ 211\right\}$ orientation for higher $\epsilon$. The predicted dependence on the reduced temperature is consistent with the respective mean field critical exponent. The results are fitted with an eight-term Kubic harmonic series, and are used to create stereographic plots displaying the anisotropy of the interface free energy. We have also derived the corresponding Wulff shapes that vary with increasing $\epsilon$ from sphere to a polyhedral form that differs from the rhombo-dodecahedron obtained previously by growing a bcc seed until reaching equilibrium with the remaining liquid

Biomass potential assessment for locating biorefinery plant in Hungary

To find a suitable site for a 150,000 metric ton dry material per year (t dm/yr) input capacity biorefinery plant in Hungary is a challenging task. Not only biomass potentials have to be assessed, competing uses, sustainability aspects, public opinion and future threats to feedstock availability should be also taken into account. As a result of our calculations, currently there is enough feedstock available for the targeted input capacity to operate in an ecologically sustainable way. However, several factors may threaten the future of feedstock availability. In the long run enhanced price competition is anticipated for biomass among biorefinery, livestock keeping, timber industry and biomass based renewable energy production. The majority of stakeholders accept in general biorefinery as a promising solution for substituting fossil based plastics, still local interests give priority to a balanced agricultural production including higher shares of husbandry

Heterogeneous nucleation of/on nanoparticles: a density functional study using the phase-field crystal model

Crystallization of supersaturated liquids usually starts by heterogeneous nucleation. Mounting evidence shows that even homogeneous nucleation in simple liquids takes place in two steps; first a dense amorphous precursor forms, and the crystalline phase appears via heterogeneous nucleation in/on the precursor cluster. Herein, we review recent results by a simple dynamical density functional theory, the phase-field crystal model, for (precursor-mediated) homogeneous and heterogeneous nucleation of nanocrystals. It will be shown that the mismatch between the lattice constants of the nucleating crystal and the substrate plays a decisive role in determining the contact angle and nucleation barrier, which were found to be non-monotonic functions of the lattice mismatch. Time dependent studies are essential as investigations based on equilibrium properties often cannot identify the preferred nucleation pathways. Modeling of these phenomena is essential for designing materials on the basis of controlled nucleation and/or nano-patterning

Farm-level environmental performance assessment in Hungary using the Green-point system

Faced with society’s increasing expectations, the European Union’s Common Agricultural Policy uses environmental management as an increasingly critical criterion in the allocation of farm subsidies, with a shift in focus from production and area-based subsidies to payments for supplying public goods. There is an increasing demand to assess the ecological and environmental performance of farms as public money spent on provision of environmental services requires justification. The objective of this research is to strengthen the basis of the concept of farm- level environmental performance assessment. Firstly we give an overview of indicator-based sustainability assessment tools. Even though there are several different tools developed globally, and the themes and indicators for the assessment of environmental performance are very similar, there are significant differences in terms of data survey among them. Secondly we describe the development and field testing of the ‘Green-point system’ developed in Hungary. This system is able to measure the environmental performance of farms and their value/ capability of providing public goods and sustaining ecosystem services through a framework of farm enterprise calculations and assessments. The Green-point system fits well into the stream of yet scarce approaches and efforts, which in several European countries aim to introduce and strengthen the so-called result-based agri-environmental schemes alongside the currently rather dominant management-based approaches. Keywords: agroecosystems, diagnosis, environmental impact assessment, evaluation methods, indicators, sustainabilit

Az Országos Környezeti Információs Rendszer (OKIR) talajdegradációs alrendszerének (TDR) kialakítása

A talajinformációs rendszer kialakításának fontos szempontja a releváns találatok megjelenítése. Az OKIR és a hozzá szervesen kapcsolódó talajos alrendszer segítségével nyomon követhető a talaj környezeti állapota, ami nagy segítséget jelent a mezőgazdasági eredetű környezeti hatások és a talajvédelmi adatszolgáltatások adat és informatikai hátterének kidolgozásában, információszolgáltatás céljából. A talajdegradációs folyamatok országos szintű elektronikus elérhetőség monitorozásának kidolgozása a következő lépés a magyarországi talajok országos szintű adatbázis nyilvántartásában

Az agrár-környezetgazdálkodási támogatási rendszer fejlesztési lehetőségei (Hogyan tovább agrár-környezetgazdálkodás?)

Az EMVA agrár-környezetgazdálkodási intézkedései sajátos irányt vettek az utóbbi időkben. Miközben ugyanis maguk az intézkedések – alapvetően előírásaik révén – környezet- és természetvédelmi célokat igyekeznek szolgálni, addig a működtetés ismert módja miatt csak részben sikerült azt elérni, hogy a jogcímek kedvezményezettjei valós környezeti (ökoszisztéma) szolgáltatásokért kapott kifizetésként értelmezzék azokat. Sokan úgy tekintenek ezekre a kifizetésekre, mintha valóban „csak” támogatások lennének, mintha egyfajta top-up-ként is lehetne értelmezni azokat. A cikk bemutatja az agrár-környezetgazdálkodási kifizetési rendszer hazai történetét, megállapítva az egyes korszakokban jelentkező problémákat. Részletesen tárgyalja azt a koncepciót, melyet a szerzők alakítottak ki a 2014-2020-as költségvetési periódusra készülő Vidékfejlesztési Program agrár-környezetgazdálkodási intézkedésére vonatkozóan. Ennek lényegét a területhasználatonként differenciált előírások adják, melyek között választva akár gazdálkodói-szintű célprogramok összeállítására is lehetőség nyílik. A javasolt rendszer a jelentősebb környezeti problémákkal rendelkező területekre fókuszálja a kifizetéseket, és nem utolsó sorban segít a gazdálkodói környezettudatosság előmozdításában is

Phase-field crystal modeling of heteroepitaxy and exotic modes of crystal nucleation

We review recent advances made in modeling heteroepitaxy, two-step nucleation, and nucleation at the growth front within the framework of a simple dynamical density functional theory, the Phase-Field Crystal (PFC) model. The crystalline substrate is represented by spatially confined periodic potentials. We investigate the misfit dependence of the critical thickness in the Stranski–Krastanov growth mode in isothermal studies. Apparently, the simulation results for stress release via the misfit dislocations fit better to the People–Bean model than to the one by Matthews and Blakeslee. Next, we investigate structural aspects of two-step crystal nucleation at high undercoolings, where an amorphous precursor forms in the first stage. Finally, we present results for the formation of new grains at the solid-liquid interface at high supersaturations / supercoolings, a phenomenon termed Growth Front Nucleation (GFN). Results obtained with diffusive dynamics (applicable to colloids) and with a hydrodynamic extension of the PFC theory (HPFC, developed for simple liquids) will be compared. The HPFC simulations indicate two possible mechanisms for GFN