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The temperature and pressure dependences of the two 35CI nuclear quadrupole resonances in BiCIs have been measured. At constant pressure, the temperature coefficients are markedly different and this difference is shown to be due to volume effects associated with different intermolecular bonding.

GRANT CALLUM GILLIES and RICHARD YULIAN CHALLIS BROWN. Can. J. Chem. 54,2266Chem. 54, (1976.Nuclear quadrupole resonance frequencies for the metal and chlorine atoms in AsC13 and SbCI; have been measured as functions of temperature and pressure. These data are analysed to obtain the isothermal volume dependences and the isochoric temperature dependences of the field gradient parameters. Existing Icnowledge of the Group V trichlorides shows that the strength of intermolecular bonding increases in the order AsC1, < SbCl; < BiC13, and this trend is reflected in the relative importance of volume effects in determining the nqr freq~lencies in these solids. A simple theory of the pressure dependences of nqr frequencies in molecular crystals is proposed, which accounts for all data presentiy available. The pressure coefficient contains static and dynamic contributions which are of opposite signs; the static contributioil is negative and becomes nulnerically larger as the strength of intermolecular bonding increases.GRANT C A L L U~~ GILL~LS et RICHARD JULIAN CHALLIS BROWN. Can. J. Chem. 518, 2266Chem. 518, (1976. On a mesure les frequences de resonance iluclCaire quadrupolaire des atomes mCtalliques et des chlores dans le AsC1; et le SbC13 en fonction de la temperature et de la pression. On a analysC ces donnCes pour obtenir des dCpendances volumiques isothermes et les dipendances isochore de tempkrature pour les paramiitres de gradient de champ. I e s connaissances existantes des trichlorures du groupe V montrent que la force des liaisons intermolCculaires augmente dans l'ordre AsCi, < SbC13 < BiC13; cette tendance se refliite dans l'importance relative des effets volumiques lors de la determination des frCquellces rilq de ces solides. On propose une thCorie simple pour expliquer la dependance entre la pression et les frkquences rnq des cristaux molCculaires; cette theorie tient compte de toutes les doililCes qui existent presentement. Ees coefficients de pression contiennent des contributions statiques et dynamiques qu.i son? de signes opposCs. La contribution statique est negative et devient numeriquement plus grande 2 mesure que la force de liaison intermolCculaii-e augmente.[Traduit par le journal]

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