Amy Y. Liu

Prediction of New Low Compressibility Solids

An empirical model and an ab initio calculation of the bulk moduli for covalent solids are used to suggest possible new hard materials. The empirical model indicates that hypothetical covalent solids formed between carbon and nitrogen are good candidates for extreme hardness. A prototype system is chosen and a first principles pseudopotential total energy calculation on the system is performed. The results are consistent with the empirical model and show that materials like the prototype can have bulk moduli comparable to or greater than diamond. It may be possible to synthesize such materials in the laboratory.

Ultrahigh-pressure melting of lead - A multidisciplinary study

Measurements of the melting temperature of lead, carried out to pressures of 1 megabar (1011 pascal) and temperatures near 4000 kelvin by means of a laser-heated diamond cell, are in excellent agreement with the results of previous shock-wave experiments. The data are analyzed by means of first principles quantum mechanical calculations, and the agreement documents the reliability of current experimental and theoretical techniques for studies of melting at ultrahigh pressures. These studies have potentially wide-ranging applications, from planetary science to condensed matter physics.

Theoretical study of the stability of cubic WC

Abstract We present the results of an ab initio pseudopotential local orbital calculation on WC in the NaCl structure (β-WC). Based on total energy calculations, β-WC is found to be less stable than the hexagonal α-phase of WC. Moreover, the calculated electronic band structure and density of states show that the instability of the NaCl structure is caused by the occupation of antibonding states. By applying the rigid band model to our results, we are able to explain trends of stability and metallicity in the cubic transition metal carbides.

Theory of Structural and Electronic Properties of Silicon Nitride and Carbon Nitride

Using a first principles pseudopotential total energy approach with a localized basis for the electronic wave functions, we have investigated the structural and bonding properties of β-Si 3 N 4 and β-C 3 N 4 , which is a proposed structure for carbon nitride. The latter system is used as a prototype for studying the properties of possible covalent C-N solids. For β-Si 3 N 4 , calculated structural properties such as lattice constant and bulk modulus are in excellent agreement with experimental values. This gives support for the predicted properties of β-C 3 N 4 .β/C 3 N 4 is found to be a good candidate for a new low-compressibility solid, with compressibility comparable to diamond. Despite similarities between β-Si 3 N 4 and β-C 3 N 4 in terms of crystal structure and valency of constituent elements, differences are found in their electronic bonding properties. A comparison of the bonding in β-Si 3 N 4 and β-C 3 N 4 with other first and second row semiconductors is useful for understanding trends in the structural properties of these materials.

Globalization and internationalization in higher education: theoretical, strategic and management perspectives

of life chances for students”. However, the author admits that strong inequalities in participation rates between those most and least likely to attend university remain. It is a timely call for more sophisticated means of decision making in addressing access inequalities that should have been considered at an earlier stage of the debate, alas this may fall on deaf ears in light of the post-Brown and New Labour agendas. The book will be of particular use to those interested in demographic and statistical dimensions to access and widening participation, as well as senior management, and those in the recruitment and marketing of courses, especially as we enter into the era of the UK post-Brown funding review and variable fees. Indeed, although this reviewer specialises in qualitative approaches to data collection, this book offers a refreshing alternative to what we normally see quite a lot of in widening participation research, that of the qualitative, sociological and small scale intervention.