iv ABSTRACTSOF PAPERSTO APPEAR IN J. PHYS. CHEM. SOLIDS Vol.7, No.18

(1150°C,1300°C,1450°C)by neutrondiffraction. J.B. Clark andE. Rapoport,ChemicalThe variationof the maximum of i(k) with tem- PhysicsGroupof the National Physicalperaturehasbeenstudiedfrom 1086°Cto 1492°C and NationalChemicalResearchand showsa linear dependencewith lIT. The Laboratories,South African Council forpair distribution functiong(r) and thedirect Scientific and IndustrialResearch,correlationfunction c(r) havebeenobtainedby P.O. Box 395, Pretor’ia, SouthAfricaFouriertransformationand the pair potentielV(r) wasderivedfrom theseusingthe Percus— Phasetransitionsin Ag2 S, Ag2Se,Ag2Te,Yevick and hypernettedchainequations.These Cu2Sand Cu2Sewerestudiedby differentialtwo approximationsarenot applicableto liquid thermal analysis(DTA) to 40kbar. The transitioncopperbut the repulsivepart of the potential is temperaturelines increasewith pressurewithin good agreementwith a hardspheremodel of initial slopesof 1.57, 6, 11.48, and0.5°C/kbar,corea = 2.2A. respectively,for the first four and—0.6°C/kbar

Received18 February1969 for (probablycopper-deficient)Cu2Se.

Revised3 June1969 Received9 May 1969

Revised30 June196911. EFFECT OF PRESSUREON SOLID—

SOLID TRANSITIONS IN SOMESILVER AND CUPROUSCHALCO-GENIDES