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.\"
.IX Title "Xray::Scattering::CromerMann 3pm"
.TH Xray::Scattering::CromerMann 3pm "2015-07-28" "perl v5.20.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Xray::Scattering::CromerMann \- Perl interface to Thomspon scattering factors
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\&  use Xray::Scattering;
\&  Xray::Scattering\->load(\*(AqCroMann\*(Aq);
\&  $fnot = Xray::Scattering\->get_f($symb, $d);
.Ve
.SH "DESCRIPTION"
.IX Header "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:
.PP
.Vb 3
\&          4
\&    f0 = sum [ ai*exp(\-bi*s^2) ] + c
\&         i=1
.Ve
.PP
Thus there are 9 coefficients for each of the 213 tabulated
element/valence symbols.
.PP
\&\f(CW\*(C`s\*(C'\fR is \f(CW\*(C`sin(theta)/lambda\*(C'\fR.  \f(CW\*(C`(lambda*s)/2pi\*(C'\fR is the momentum
transfer.  \f(CW\*(C`s\*(C'\fR is simply related to the crystal d\-spacing by
\&\f(CW\*(C`s=1/2d\*(C'\fR.
.PP
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.
.PP
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.
.SH "CLASS METHODS"
.IX Header "CLASS METHODS"
.ie n .IP """get_f""" 4
.el .IP "\f(CWget_f\fR" 4
.IX Item "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.
.Sp
.Vb 2
\&  $symb = "Ce3+";
\&  $fnot = Xray::Scattering\->get_f($symb, $d);
.Ve
.Sp
If the symbol cannot be found in the table, \f(CW\*(C`get_f\*(C'\fR returns 0.  It
also returns 0 when \f(CW$symbol\fR consists of whitespace or is \*(L"null\*(R" or
\&\*(L"nu\*(R".  If \f(CW$symbol\fR is a number or the name of an element, then it
assumes you want the Thomson scattering for the neutral element.  The
absolute value of \f(CW$d_spacing\fR is used by this function.
.Sp
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.
.ie n .IP """get_coefficients""" 4
.el .IP "\f(CWget_coefficients\fR" 4
.IX Item "get_coefficients"
This returns the 9 element list containing the coefficients for the
given symbol.
.Sp
.Vb 1
\&   @coefs = Xray::Scattering\->get_coefficients($elem)
.Ve
.Sp
Returns the array a1,b1,a2,b2,a3,b3,a4,b4,c.
.Sp
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.
.ie n .IP """has""" 4
.el .IP "\f(CWhas\fR" 4
.IX Item "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.
.Sp
.Vb 2
\&  $symb = "Ce3+";
\&  $is_tabulated = Xray::Scattering\->has($symb);
.Ve
.SH "ELEMENTS AND VALENCE STATES"
.IX Header "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).
.PP
.Vb 10
\&      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\-.   \*(Aq \*(Aq    Nu
.Ve
.SH "AUTHOR"
.IX Header "AUTHOR"
.Vb 2
\&  Bruce Ravel, bravel AT bnl DOT gov
\&  http://cars9.uchicago.edu/~ravel/software/exafs/
.Ve