Dear all,

Just as a historic reminder, I feel necessary to mention a key article on refinement, written by R.Aragwal (1978) in Acta Cryst A, where he used 1- and 2-gaussian atomic factors (obviously, less precise that 4 gaussians + constant but allowed him at that moment to accelerate as much as possible the calculations).

With best regards,

Sacha Urzhumtsev

De : CCP4 bulletin board [mailto:[log in to unmask]] De la part de Pavel Afonine
Envoyé : jeudi 3 novembre 2011 04:40
À : [log in to unmask]
Objet : Re: [ccp4bb] atomic scattering factors in REFMAC

Continuing on the subject, as far as I know there are at least three flavors of form-factors currently used in refinement programs:

"4 gaussian plus const":

International Tables for Crystallography (1992)

"5 gaussian plus const":

D. Waasmaier & A. Kirfel. Acta Cryst. (1995). A51, 416-431. "New analytical scattering-factor functions for free atoms and ions"

"n-gaussian" (n determined dynamically)

Grosse-Kunstleve RW, Sauter NK & Adams PD. Newsletter of the IUCr Commission on Crystallographic Computing 2004, 3:22-31. "cctbx news"

All three are available in PHENIX (the 3rd is used by default), and I presume the first one is used in CNS and Refmac, if I remember correctly (the authors of respective programs please correct me).

Pavel