Reflection Data Analysis Tools in PLATON Problem from Bruker Discussion List: Triclinic or Monoclinic? Ni-complex In P-1,Z'=2: a = b = c = Alpha = Beta = Gamma = R1 = 10% WR2 = 31% Ton Spek, Utrecht University, The Netherlands Bruker User Meeting Bad Herrenalb, Sept. 23, 2012

Triclinic, Monoclinic ? -The New SHELXT program offers a starting model in P-1 and Pn and P21/n -PLATON/ADDSYM happily offers a structure in P21/n that resembles the solution in P-1

Alternative Monoclinic Model In P21/n, Z'=1: A = B = C = Alpha = 90 Beta = Gamma = 90 R1 = 17% WR2 = 53% Poor ADP's

Monoclinic Model ADP's

Looking at the Data - Investigate thePrimary Data - Images, Integration - HKL File - Redundancy, Laue Symmetry (Rav) - Space Group Extinctions - Investigate the Refinement Data - Analysis of Variance - Twinning With Tools Available in PLATON

Test P-1 Model for Twinning

Overlapped k = 0 Layer

Rav (Monoclinic – 2/m) = 21% on F(calc) Model

Refined Model in P-1 All H-atoms Found and rerined

In Conclusion -Three additional parameters had to be introduced to obtain a nice looking refinement result in P-1: -- A twinning parameter -- Two population parameters Ni1 0.88, Ni The residual problem: explain the non 1.0 population parameters for Ni. - Go back to the chemist …..

Thanks ! Example taken from the very active and interesting Bruker User Discussion List Maintained by Ilia Guzai Problem and data communicated by Babu Varghese