The equilibrated grain boundary groove shapes for the commercial purity succinonitrile (SCN) and succinonitrile-carbon tetrabromide (CTB) eutectic system were directly observed. From the observed grain boundary groove shapes, the Gibbs-Thomson coefficients for the solid SCN-liquid SCN and solid SCN-liquid SCN CTB have been determined to be (5.43 +/- 0.27) x 10(-8) Km and (5.56 +/- 0.28) x 10(-8) Km, respectively, with numerical method. The solid-liquid interface energies for the solid SCN-liquid SCN and solid SCN-liquid SCN CTB have been obtained to be (7.86 +/- 0.79) x 10(-3) J m(-2) and (8.80 +/-0.88) x 10(-3) J m(-2), respectively from the Gibbs-Thomson equation. The grain boundary energies in the SCN and SCN rich phase of the SCN-CTB system have been calculated to be (15.03 +/- 1.95) x 10(-3) J m(-2) and (16.51 +/- 2.15) x 10(-3) J m(-2), respectively, from the observed grain boundary groove shapes. The thermal conductivity ratios of the liquid phase to the solid phase for SCN and SCN-4 mol% CTB alloy have also been measured. (C) 2002 Elsevier Science B.V. All rights reserved.