HIGH-PRESSURE STUDIES WITH KUMA. Damian Kucharczyk and Andrzej Katrusiak⁺, KUMA Diffraction, Akacjowa 15b, 53-122 Wroclaw, Poland; ⁺Department of Crystal Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan

A new programme for measuring reflection intensities of the crystals enclosed in high-pressure diamond-anvil cells of the Merrill-Bassett type has been prepared for the KUMA diffractometers. The main objective was to minimize the effects of high-pressure cell absorption [L.W.Finger and H.King, Am. Mineralog. 63 (1978) 337], and of the extinction of the diamond anvils [J.S.Loveday, M.I.McMahon and R.J.Nelmes, J. Appl.Cryst. 23 (1990) 392], without significantly prolonging the data collections. The programme contains several options allowing one to tackle the experimental difficulties. It is also aimed at facilitating the high pressure studies. It was demonstrated, that good quality structural data of the accuracy comparable to those from ambient-pressure measurements on bare crystals could be obtained in the preliminary high-pressure study on pentaerithritol, i.e. 2,2-bis(hydroxymethyl)-1,3-propanediol, crystals [A.Katrusiak, Acta Crystallogr. B51 (1995) 873].