INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS: CONDENSED MATTER J. Phys.: Condens. Matter 16 (2004) 195–222 PII: S0953-8984(04)70750-X Structure of liquid lithium Philip S Salmon 1 , Ingrid Petri 1 , Paul H K de Jong 2 , Peter Verkerk 3,6 , Henry E Fischer 4 and W Spencer Howells 5 1 Department of Physics, University of Bath, Bath BA2 7AY, UK 2 H HWills Physics Laboratory, University of Bristol, Royal Fort, Tyndall Avenue, Bristol BS8 1TL, UK 3 Interfacultair Reactor Instituut, Technische Universiteit Delft, Mekelweg 15, 2629 JB Delft, The Netherlands 4 LURE, Centre Universitaire Paris-Sud, BP 34, F-91898, Orsay C´ edex, France 5 ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK Received 16 October 2003 Published 9 January 2004 Online at stacks.iop.org/JPhysCM/16/195 (DOI: 10.1088/0953-8984/16/3/002) Abstract Neutron diffraction experiments, made at a steady-state reactor source, were used to study the structure of liquid 7 Li at temperatures of 197, 452 and 595 ◦ C. A careful data analysis procedure was undertaken in which specific issues taken into account include (i) the influence of Brillouin modes on the measured diffraction pattern at small scattering vectors, (ii) inelasticity corrections that are significant for light atom systems, such as lithium, and (iii) the effects caused by the diffractometer resolution function. Data sets taken for the same liquid temperature using different incident neutron energies yield ion–ion partial structure factors, S II (k ), that are in agreement within the statistical errors. The S II (k ) are compared with previous experimental results and with the results obtained from liquid state theory and molecular dynamics methods made using several different local pseudopotentials. Finally, the valence electron form factor, ρ(k ), is estimated by combining S II (k ) with x-ray diffraction data and the ion–valence electron partial structure factor, S Ie (k ), is calculated by combining S II (k ) with the ρ(k ) obtained from both experiment and theory. The results show that the extraction of ρ(k ) and S Ie (k ) by a combination of neutron and x-ray diffraction methods is feasible in practice, but demonstrates a need for new x-ray diffraction experiments on liquid lithium. 1. Introduction Liquid lithium has an electronic structure, 1s 2 2s, which gives it a larger ratio of valence to core electrons than for all other metals, with the exception of beryllium which is, however, an extremely difficult material to study in the liquid phase owing, for example, to its high melting 6 Deceased. 0953-8984/04/030195+28$30.00 © 2004 IOP Publishing Ltd Printed in the UK 195