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Single-phase Pr 2 CBr was prepared by heating a mixture of PrBr 3 , Pr and C (1 : 5:3) to 1140 • C for 18 d. The crystal structure was investigated by X-ray single crystal diffraction (space group P6 3 /mmc, a = 3.8071 (3), c = 14.7787(12)Å). In the structure the Pr atoms form C-centered octahedra condensed into Pr 2 C sheets via common edges; these sheets are separated by the Br atoms which are in a trigonal prismatic environment of Pr atoms. Pr 2 CBr is a black shiny compound with metallic conductivity. It is a ferromagnet with T c = 13.8(5) K.

Computer simulations of star-branched and linear polymers in spherical pores were performed in order to estimate their GPC-distribution coefficients. Based on these simulations, correction factors can be estimated, that allow correcting for the underestimation of the molecular weight of branched polymers if evaluated using a calibration curve based on linear standards.The results of the computer simulations were compared with experimental results of GPC-light scattering experiments of star polymers having of defined arm-numbers and arm-molecular weights. Good qualitative and quantitative agreement was found between experimental and simulated correction factors.The simulations were used additionally to elucidate the structure of coupling peaks in ATRP with multifunctional initiators. The elution volumes of these peaks were in good agreement with an expected dumbbell topology that would arise from arm-arm coupling of different stars.The authors would like to express their gratitude to Prof. A. Hirao, Tokyo Institute of Technology and PSS Polymer Standards Service GmbH, Mainz for supplying samples.