The crystalline and magnetic structures of the YCo 3 -H͑D͒ system have been investigated by means of x-ray and neutron diffraction with the objective of understanding the complex magnetic changes that are observed in this system as hydrogen is added. Synchrotron x-ray diffraction ͑XRD͒ patterns were first refined to yield the lattice parameters and coordination of Y and Co atoms in the metal and two ␤-hydride phases while XRD was used for the ␥ phase. In situ neutron powder diffraction measurements of YCo 3 D x were then made in all four phases to determine the deuterium site occupancies and magnetic structures. The site occupancies were also rationalized using the Westlake geometric model. The highest hydrogen concentration measured was YCo 3 H 4.6 . Using the Westlake model, we conclude that the saturated hydrogen content would be YCo 3 H 5 . Our results reported here and in Part I ͓Phys. Rev. B 76, 184443 ͑2007͔͒ have enabled us to rationalize the changes in the magnetic structures in terms of changes in the cobalt-cobalt distance caused by the addition of hydrogen. In particular, in the antiferromagnetic ␥ phase, we observe Co atomic displacements that enable the structure to adopt a particular antiferromagnetic structure in a manner that is reminiscent of a Peierls distortion as observed in transitions from the conducting to nonconducting hydrides on addition of hydrogen in YH 3 .

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We review the 2014 International Planning Competition (IPC-2014), the eighth in a series of competitions starting in 1998. IPC-2014 was held in three separate parts to assess state-of-the-art in three prominent areas of planning research: the deterministic (classical) part (IPCD), the learning part (IPCL), and the probabilistic part (IPPC). Each part evaluated planning systems in ways that pushed the edge of existing planner performance by introducing new challenges, novel tasks, or both. The competition surpassed again the number of competitors than its predecessor, highlighting the competition’s central role in shaping the landscape of ongoing developments in evaluating planning systems.

We report a direct comparison of the local structure of the hydrophobic hydration of krypton in both the liquid and solid states by the extended x-ray absorption fine structure spectroscopy technique. The evolution of an ordered hydration shell of the nonpolar gas moiety is followed as the liquid to solid phase transition progresses. The formation of a clathrate cage structure from the more disordered liquid state hydration shell is clearly demonstrated. [S0031-9007(98)07579-6] PACS numbers: 61.25. Em, 61.10.Ht, 64.70.Dv Gas hydrates are an interesting and very important class of materials that often display unusual properties [1]. The structural processes involved in the formation of these materials are currently a topic of great interest for many reasons; for example, there are significant quantities of valuable natural gas resources stored in this form [2].The crystalline structures of the gas hydrates have been well characterized. Generally the structures are of the cagelike type-I or type-II clathrate structures, depending upon the size of the "guest" gas molecules [3,4], and which stabilize the lattice through nonbonding repulsive interactions [5,6]. These structures have a principle building block which is the pentagonal dodecahedron of radius 3.9 Å. As this is not a space filling polyhedron, the crystalline form of these hydrates contains a second (larger) polyhedra to form the lattice [4]. Though the type-I structure has a smaller large cage size than type II, the smallest guests, e.g., argon, krypton, and oxygen, tend to form the latter, probably because the ratio of small to large cages is higher [7].Here we report an investigation of the hydrate formation process using extended x-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS probe is intrinsically short ranged and element specific; in this case we investigate the local structure around krypton atoms on either side of the liquid to solid phase transition, where the structural signal is dominated by krypton to water oxygen correlations. EXAFS is an ideal microscopic probe for the comparison of the local structure around the Kr atom in the two phases due to its insensitivity to the onset of the long range order in the crystalline phase.The structural nature of nonpolar gas hydration is particularly relevant to the still controversial topic of hydrophobic hydration and the associated hydrophobic effect, by which nonpolar solute moieties associate in the aqueous environment. The direct comparison of the local structure between the liquid state and solid state hydration of a nonpolar gas provided by this experimental study allows us to make a direct evaluation of the oftenmisinterpreted iceberg model of hydrophobic hydration suggested by Frank and Evans in 1945 [8]. They postulated that the water hydrating such solutes might be perturbed in the direction of greater crystallinity when compared with that found in the pure bulk solvent.This model [8] has subsequently generated a great deal of interest among experimental and theoretical worke...

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