Dear All thank you very much for all your emails. Let me summarize: dear Jon if I have understood well, you are telling me that no lattice distortion can give me that splitting of the 006 peak, even if a structural transition changes the space group R-3c to another one. Am I right?
About the possibility of an experimental artifact due to a temperature instability, I can exclude it, because it would produce also a splitting of the peaks with the a-axis component, which I don't see at all. In fact I have some low resolution data that shows that the a-axis varies quite a lot with temperature. So in base of your opinion the only possible explanation would be "phase segregation" or "exsolution"? thank you again for your help best regards Stefano Quoting Kurt Leinenweber <[EMAIL PROTECTED]>: > Hi all, > > All I can think of is an exsolution of some type. But, this seems > difficult to imagine at a low temperature such as this. > > - Kurt > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] > Sent: Tuesday, May 22, 2007 12:29 PM > To: Jon Wright > Cc: [email protected] > Subject: Re: peaks splitting > > OOOPSSS! True: 006 can't split! > I just overlooked the hkl's of the split peak. > Needless to say, I should have read the message more carefully... > Norberto Masciocchi > > Quoting Jon Wright <[EMAIL PROTECTED]>: > > > Hi everyone, > > > > Three responses saying it might be a lower spacegroup? I wonder if the > > emperors have their clothes on today? > > > > (006) reflections can't split in R-3c as they only have a multiplicity > > of 2 in the first place (0,0,6 and 0,0,-6). You were lucky enough to > > split (00l) which rules out any lattice distortion. Or lots of people > > are about to shout at me. > > > > Either a paper about "phase segregation" or an experimental artifact > > like a temperature instability. Or both! > > > > Cheers, > > > > Jon > > > > [EMAIL PROTECTED] wrote: > >> Dear all > >> I need your kind help > >> I am investigating a trigonal system. I collected neutron diffraction > >> patterns at T=300K and T=4K. > >> The data at T=300K can be nicely fitted with the spg R-3c. > >> At T=4K again I can described the data with the spg R-3c, but I > >> noticed that now > >> the peaks with a larger c-axis component (see the (006) peak picture > in > >> attachment) are splitted in two: it is like as at low temperature > >> there are two > >> phases with different c-axis (10.5838 and 10.566 Amstrong) and same > a-axis. > >> I don't think that the sample is chemically phase separated because > at room > >> temperature the (006) reflection is clearly a single peak. The > splitting > >> appears only at low temperature. > >> > >> Could anyone suggest me any possible explanation of this splitting > (lattice > >> distortion, modulation, etc)? Could be possible a triclinic > distortion? > >> > >> I don't know how to fit the data at T=4K. Should I change the space > group > >> because now I have two peaks while the R-3c gives me only one peak? > Then by > >> which criteria should I choose the new space group? > >> > >> thank you very very very much for your advices > >> > >> > >> best regards > >> > >> Stefano Agrestini > >> > >> Physics Department > >> The University of Warwick, UK > >> > >> ---------------------------------------------------------------- > >> This message was sent using IMP, the Internet Messaging Program. > >> > >> > >> > ------------------------------------------------------------------------ > >> > > > > ---------------------------------------------------------------- > This message was sent using IMP, the Internet Messaging Program. > > > > > ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.
