iv ABSTRACTSOFARTICLESTO APPEARIN J.PHYS. CHEM. SOLIDS Vol. 25,No. 12

3. SILVER ATOM CENTERIN a-QUARTZ respectto oneparticularlatticeparameter,leaving

P.H. Davisand i.A. Well, Departmentof invariantall internaldistancesin the polyatomicions.ChemistryandChemicalEngineering, Received11 July 1977Universityof Saskatchewan,Saskatoon, Revised4 January1978Sask.S7NOWO, Canada.

A newparamagneticcenter,A Ag—Si’ in silver-diffuseda-quartzis describedandits spin-Hamiltonian 6. MODEL OF INSTABILITIES IN PdHXparametersare presented.The centeris formulatedas a AND PdDXsilver atom (S= 1/2) situatedin a c-axischannel, K.L. Ngai andT.L. Reinecke,Naval Researchbondedweaklyto a normalsilicon cation,with four Laboratory,Washington,D.C. 20375,U.S.A.oxygenanionsasneighbors.A ~ is createdbyX-irradiation,andis unstableat room temperature. Theinstability andinhomogeneityof the PdHX and

PdDX systemsis discussed.A simplemodel basedon theReceived27 September1977 existenceof more than onelocal electronicandionic

configurationis proposed,and theresultsof this modelareshownto be consistentwith severalimportant

4. ELASTIC PROPERTIESOFDILUTE lattice propertiesof thesesystemsincludinga differencePALLADIUM—HYDROGEN SOLID betweenthePd—HandPd—Dforce constants.

SOLUTIONSReceived18 July 1977R.J.FarraroandRex B. McLellan,Department

of MaterialsScience,William MarshRiceUniversity,Houston,TX 77001,U.S.A.

7. SIMULTANEOUSDIFFUSIONOF CALCIUMA thin-linepulse-echotechniquehasbeenusedto AND STRONTIUM IN KC1 SINGLE

measurethevariationof theYoung’smodulusof super- CRYSTALSpurepalladiumasa function of temperatureandhydro-

H. MachidaandW.i. Fredericks,Departmentofgenconcentration.

Theresultingmeasurementshavebeenanalyzedso Chemistry,OrigonStateUniversity,Corvallis,OR97331,U.S.A.

asto yield approximateinformationrelating to thechangeto beexpectedin the partialthermodynamic Concentrationdependentdiffusion coefficientsforfunctionsof the systemdueto thelattice relaxationat 45Sr21’ in purified KCI weremeasuredusinga sectioningconstantpressure. method.KC1 waspurified by anion exchange—C1

2—HC1

Received21 November1977 processandthecrystalsgrown under1/6 atmosphereofRevised4 January1978 HC1. The tracerswerepurified on smalldisposableion

exchangecolumnsto removeprecessoranddaughterimpuritiesprior to use in a diffusionanneal.Isothermal

5. EXPANSIONOFTHE MADELUNG diffusion annealswere madein the temperaturerangePARAMETERIN TERMS OFMULTIPOLE from 451 to 669°C.At temperaturesabove580°C(theMOMENTS AND AS A FUNCTION OF THE lowestmeltingeutecticin this system)diffusion wasRATIO OFTWO LATTICE PARAMETERS from a vaporsource;below 580°Csurfacedeposited

sourceswere used.Thesaturationdiffusion coefficients,P. Herzig andA. Neckel,Institut für enthalpiesandentropiesof impurity—vacancyTechnischeElektrochemiederTechnischen, associationswere calculatedusingthe commonionUniversitätWien, Getreidemarkt9, A-1060 modelfor simultaneousdiffusion of divalentionsinVienna,Austria. alkali halides.In KC1 thesaturationdiffusion

A methodis derivedto expandtheMadelung coefficientsD8(Ca)andD8(Sr)aregiven byparametersof non-cubiccrystalsas a functionof the Ds(Ca) = 9.93 x l0~exp(— 0.592eV/kT)cm

2/sec (1)ratio of two lattice parametersandin termsof multipolemoments.Only oneexpansionof this kind is necessary andto evaluatethe Madelungconstantsfor a seriesof D~(Sr)= 1.20 x l0~exp(—0.871eV/kT)cm2/sec (2)compoundsof onetype of structureeithercontainingpolyatomicionsor sphericalionsat positionsslightly for calciumandstrontium,respectively.TheGibbsfreevaryingfrom onecompoundto the other. Thismethod energyof associationof the impurity vacancycomplexalsoallows the minimisationof the lattice energywith in KU for calciumcanbe representedby