Xray::Scattering::CromerMann(3pm)			User Contributed Perl Documentation			 Xray::Scattering::CromerMann(3pm)

NAME

       Xray::Scattering::CromerMann - Perl interface to Thomspon scattering factors

SYNOPSIS

	 use Xray::Scattering;
	 Xray::Scattering->load('CroMann');
	 $fnot = Xray::Scattering->get_f($symb, $d);

DESCRIPTION

       This module provides a functional interface to the Cromer-Mann table of coefficients for calculating the Thomson (kinematical) scattering
       factors of the elements and common valence states.  The coefficients are stored externally in the cromann.db database file.  The
       coefficients are for an Aikman expansion, which is of this form:

		 4
	   f0 = sum [ ai*exp(-bi*s^2) ] + c
		i=1

       Thus there are 9 coefficients for each of the 213 tabulated element/valence symbols.

       "s" is "sin(theta)/lambda".  "(lambda*s)/2pi" is the momentum transfer.	"s" is simply related to the crystal d-spacing by "s=1/2d".

       The data for these tables can be found in Volume C of the International Tables of Crystallography, ed. A.J.C. Wilson, published by IUCr and
       Kluwer Academic Publishers(1992).  The table starts on page 500 and a discussion can be found on page 487.

       These tables are known to be inaccurate, particularly at high angles.  This module is a toy.  It is suitable for a student or for the sort
       of quick-n-dirty crystallographic hackery that the author indulges in.

CLASS METHODS

       "get_f"
	   This function calculates the Thomson scattering for a given symbol and d-spacing.  The Thomson scattering depends only on the momentum
	   transfer.  The d-spacing of the scattering planes is a closely related quantity and is easily calculated from the crystal structure,
	   see Xtal.pm.

	     $symb = "Ce3+";
	     $fnot = Xray::Scattering->get_f($symb, $d);

	   If the symbol cannot be found in the table, "get_f" returns 0.  It also returns 0 when $symbol consists of whitespace or is "null" or
	   "nu".  If $symbol is a number or the name of an element, then it assumes you want the Thomson scattering for the neutral element.  The
	   absolute value of $d_spacing is used by this function.

	   If you ask for a valence state that is not in the table but for an element whose 0+ state is in the table, this method returns the
	   scattering factor for the 0 valent atom.

       "get_coefficients"
	   This returns the 9 element list containing the coefficients for the given symbol.

	      @coefs = Xray::Scattering->get_coefficients($elem)

	   Returns the array a1,b1,a2,b2,a3,b3,a4,b4,c.

	   If you ask for a valence state that is not in the table but for an element whose 0+ state is in the table, this method returns the
	   coefficients for the 0 valent atom.

       "has"
	   This is a test of whether a given symbol is tabulated in the Cromer-Mann table.  It returns the symbol itself if found in the table or
	   0 if it is not in the table.

	     $symb = "Ce3+";
	     $is_tabulated = Xray::Scattering->has($symb);

ELEMENTS AND VALENCE STATES

       The following is a list of symbols for the tabulated elements and valence states.  The final two are ways of refering to an empty site
       (i.e. a null or blank atom).

	     H	    H.	   H1-	  He	 Li	Li1+   Be
	     Be2+   B	   C	  C.	 N	O      O1-
	     F	    F1-    Ne	  Na	 Na1+	Mg     Mg2+
	     Al     Al3+   Si	  Si.	 Si4+	S      P
	     Cl     Cl1-   Ar	  K	 K1+	Ca     Ca2+
	     Sc     Sc3+   Ti	  Ti2+	 Ti3+	Ti4+   V
	     V2+    V3+    V5+	  Cr	 Cr2+	Cr3+   Mn
	     Mn2+   Mn3+   Mn4+   Fe	 Fe2+	Fe3+   Co
	     Co2+   Co3+   Ni	  Ni2+	 Ni3+	Cu     Cu1+
	     Cu2+   Zn	   Zn2+   Ga	 Ga3+	Ge     Ge4+
	     As     Se	   Br	  Br1-	 Kr	Rb     Rb1+
	     Sr     Sr2+   Y	  Y3+	 Zr	Zr4+   Nb
	     Nb3+   Nb5+   Mo	  Mo3+	 Mo5+	Mo6+   Tc
	     Ru     Ru3+   Ru4+   Rh	 Rh3+	Rh4+   Pd
	     Pd2+   Pd4+   Ag	  Ag1+	 Ag2+	Cd     Cd2+
	     In     In3+   Sn	  Sn2+	 Sn4+	Sb     Sb3+
	     Sb5+   Te	   I	  I1-	 Xe	Cs     Cs1+
	     Ba     Ba2+   La	  La3+	 Ce	Ce3+   Ce4+
	     Pr     Pr3+   Pr4+   Nd	 Nd3+	Pm     Pm3+
	     Sm     Sm3+   Eu	  Eu2+	 Eu3+	Gd     Gd3+
	     Tb     Tb3+   Dy	  Dy3+	 Ho	Ho3+   Er
	     Er3+   Tm	   Tm3+   Yb	 Yb2+	Yb3+   Lu
	     Lu3+   Hf	   Hf4+   Ta	 Ta5+	W      W6+
	     Re     Os	   Os4+   Ir	 Ir3+	Ir4+   Pt
	     Pt2+   Pt4+   Au	  Au1+	 Au3+	Hg     Hg1+
	     Hg2+   Tl	   Tl1+   Tl3+	 Pb	Pb2+   Pb4+
	     Bi     Bi3+   Bi5+   Po	 At	Rn     Fr
	     Ra     Ra2+   Ac	  Ac3+	 Th	Th4+   Pa
	     U	    U3+    U4+	  U6+	 Np	Np3+   Np4+
	     Np6+   Pu	   Pu3+   Pu4+	 Pu6+	Am     Cm
	     Bk     Cf	   O2-.   ' '	 Nu

AUTHOR

	 Bruce Ravel, bravel AT bnl DOT gov
	 http://cars9.uchicago.edu/~ravel/software/exafs/

perl v5.12.4							    2011-07-30					 Xray::Scattering::CromerMann(3pm)