The computer simulation of the structure of point defects in copper.

The atomic structures and formation energies and volumes of a copper crystal for a series of single and multiple point defects have been calculated by real-space computer modelling techniques. Stable and metastable defect configurations were obtained by iteratively minimizing the potential energy of the model crystal. The interaction between atoms was described by three new, short-ranged, central, 'non-equilibrium' pair-potentials. Each potential was derived in such a manner that they reproduce exactly the experimental lattice parameter, the three elastic constants c[11], c[12] and c[44] and the vacancy formation and intrinsic stacking fault energies. The potentials differ only at those separations which are less than the first nearest-neighbour distance in copper. Two types of single vacancies and nine different kinds of single interstitials were simulated with each of the potentials. The normal vacancy consisting of an empty lattice site is stable whilst the split vacancy comprising two nearest-neighbour vacant sites and an atom between them is unstable. The nine interstitial configurations studied are the octahedral, tetrahedral, crowdion, octahedral-tetrahedral, octahedral-crowdion, tetrahedral-crowdion, split , split and split types. For the softest potential all of the interstitials are equilibrium structures but for the other two the tetrahedral-crowdion is unstable. In each case the tetrahedral interstitial is the stable one. The stability of vacancy pairs and close-packed clusters of trivacancies and tetravacancies were studied using the potential in best agreement with experimentally determined single vacancy properties. All four of the possible clusters of trivacancies relax to equilibrium configurations. The stable trivacancy structure is formed from a tetrahedron of nearest-neighbour vacant sites enclosing at its centre an atom displaced from one of the empty sites. Of the twenty different tetravacancies clusters investigated six were either stable or metastable. The lowest energy configuration is derived from the square of tetravacancies which relaxes to an octahedral cage of six vacancies surrounding two interstitials lying on the long axis of the octahedron. The distance between the interstitials is close to the first nearest-neighbour separation in copper

The computer simulation of the structure of point defects in copper.

The atomic structures and formation energies and volumes of a copper crystal for a series of single and multiple point defects have been calculated by real-space computer modelling techniques. Stable and metastable defect configurations were obtained by iteratively minimizing the potential energy of the model crystal. The interaction between atoms was described by three new, short-ranged, central, 'non-equilibrium' pair-potentials. Each potential was derived in such a manner that they reproduce exactly the experimental lattice parameter, the three elastic constants c[11], c[12] and c[44] and the vacancy formation and intrinsic stacking fault energies. The potentials differ only at those separations which are less than the first nearest-neighbour distance in copper. Two types of single vacancies and nine different kinds of single interstitials were simulated with each of the potentials. The normal vacancy consisting of an empty lattice site is stable whilst the split vacancy comprising two nearest-neighbour vacant sites and an atom between them is unstable. The nine interstitial configurations studied are the octahedral, tetrahedral, crowdion, octahedral-tetrahedral, octahedral-crowdion, tetrahedral-crowdion, split , split and split types. For the softest potential all of the interstitials are equilibrium structures but for the other two the tetrahedral-crowdion is unstable. In each case the tetrahedral interstitial is the stable one. The stability of vacancy pairs and close-packed clusters of trivacancies and tetravacancies were studied using the potential in best agreement with experimentally determined single vacancy properties. All four of the possible clusters of trivacancies relax to equilibrium configurations. The stable trivacancy structure is formed from a tetrahedron of nearest-neighbour vacant sites enclosing at its centre an atom displaced from one of the empty sites. Of the twenty different tetravacancies clusters investigated six were either stable or metastable. The lowest energy configuration is derived from the square of tetravacancies which relaxes to an octahedral cage of six vacancies surrounding two interstitials lying on the long axis of the octahedron. The distance between the interstitials is close to the first nearest-neighbour separation in copper

Cartographic, geophysical and diver surveys of the medieval town Site at Dunwich, Suffolk, England

This paper presents the results of an integrated historical and geophysical survey of a medieval town lost through cliff recession and coastal inundation. Key objectives included evaluating historic maps in supporting the relocation and identification of major buildings, and applying integrated multibeam, side-scan and sub-bottom profiling to determine the location and extent of archaeological remains. The results demonstrate that cartographic sources from 1587 onwards can be a reliable source of data to guide geophysical survey. Integration of historical mapping with geophysical data enabled identification of the remains of two medieval structures, and the tentative identification of two others

Conventional and chemical munitions dumpsites in waters >200 m in the OSPAR region (OSPAR, 2005) [28].

<p>Conventional and chemical munitions dumpsites in waters >200 m in the OSPAR region (OSPAR, 2005) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012730#pone.0012730-OSPAR5" target="_blank">[28]</a>.</p

Spatial extent and confidence rating of activities.

<p>Estimates of the spatial extent of six major human activities occurring directly on the sea floor, including structures and artefacts present on the seafloor resulting from past activities, within the OSPAR maritime area of the North East Atlantic in waters >200 m during 2005. Estimates for bottom trawling and marine scientific research are based on 2005 data only.</p><p>wd: water depth;</p>†<p>Confidence ratings indicate whether the spatial extent of each activity is based on data or estimates of location and extent (Eastwood et al., 2007) <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012730#pone.0012730-Eastwood1" target="_blank">[19]</a>: 1, estimated location and estimated extent; 2 known location, estimated extent; 3, known location and extent.</p><p>*Carter et al., 2009 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012730#pone.0012730-Carter1" target="_blank">[23]</a>.</p>1<p>Information from NPD and Statoil datasets and Eastwood et al., 2007 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0012730#pone.0012730-Eastwood1" target="_blank">[19]</a>.</p>2<p>Overlapping boundaries merged.</p>3<p>SERPENT Project, unpublished data.</p