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2% $Id$
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4\label{sec:property}
5
6Properties can be calculated for both the Hartree-Fock and DFT wave
7functions. The properties that are available are:
8
9\begin{itemize}
10\item Natural bond analysis
11\item Dipole, quadrupole, and octupole moment
12\item Mulliken population analysis and bond order analysis
13\item Electrostatic potential (diamagnetic shielding) at nuclei
14\item Electric field and field gradient at nuclei
15\item Electron and spin density at nuclei
16\item NMR shielding (GIAO method)
17\item NMR hyperfine coupling (Fermi-Contact and Spin-Dipole expectation values)
18\item NMR indirect spin-spin coupling
19\end{itemize}
20
21The properties module is started when the task directive
22\verb+TASK <theory> property+ is defined in the user input file. The input
23format has the form:
24
25\begin{verbatim}
26  PROPERTY
27    [property keyword]
28    [CENTER ((com || coc || origin || arb <real x y z>) default coc)]
29  END
30\end{verbatim}
31
32Most of the properties can be computed for Hartree-Fock
33(closed-shell RHF, open-shell ROHF, and open-shell UHF), and DFT
34(closed-shell and open-shell spin unrestricted) wavefunctions. The NMR
35chemical shift is limited to closed-shell wave functions, whereas the NMR
36hyperfine and indirect spin-spin coupling require a UHF or ODFT wave function.
37
38\section{Property keywords}
39
40Each property can be requested by defining one of the following keywords:
41
42\begin{verbatim}
43  NBOFILE
44  DIPOLE
45  QUADRUPOLE
46  OCTUPOLE
47  MULLIKEN
48  ESP
49  EFIELD
50  EFIELDGRAD
51  ELECTRONDENSITY
52  HYPERFINE
53  SHIELDING [<integer> number_of_atoms <integer> atom_list]
54  SPINSPIN [<integer> number_of_pairs <integer> pair_list]
55  AIMFILE
56  ALL
57\end{verbatim}
58
59The ``{\tt ALL}'' keyword generates all currently available properties.
60
61Both the NMR shielding and spin-spin coupling have additional optional
62parameters that can be defined in the input. For the shielding the user
63can define the number of atoms for which the shielding tensor should be
64calculated, followed by the list of specific atom centers. In the case
65of spin-spin coupling the number of atom pairs, followed by the atom
66pairs, can be defined (i.e., spinspin 1 1 2 will calculate the coupling
67for one pair, and the coupling will be between atoms 1 and 2).
68
69For both the NMR spin-spin and hyperfine coupling the isotope that has
70the highest abundance and has spin, will be choosen for each atom under
71consideration.
72
73The user also has the option to choose the center of expansion for
74the dipole, quadrupole, and octupole calculations.
75
76\begin{verbatim}
77    [CENTER ((com || coc || origin || arb <real x y z>) default coc)]
78\end{verbatim}
79
80\verb+com+ is the center of mass, \verb+coc+ is the center of charge, \verb+origin+ is
81(0.0, 0.0, 0.0) and \verb+arb+ is any arbitrary point which must be accompanied
82by the coordinated to be used.  Currently the x, y, and z coordinates
83must be given in the same units as \verb+UNITS+ in \verb+GEOMETRY+ (See Section
84\ref{sec:geomkeys}).
85
86\subsection{Nbofile}
87\label{sec:Nbofile}
88
89The keyword {\tt NBOFILE} does not execute the Natural Bond Analysis
90code, but simply creates an input file to be used as input to the
91stand-alone NBO code.  All other properties are calculated upon
92request.
93
94Following the successful completion of an electronic structure
95calculation, a Natural Bond Orbital (NBO) analysis may be carried out
96by providing the keyword \verb+NBOFILE+ in the \verb+PROPERTY+ directive.
97NWChem will query the rtdb and construct an ASCII file,
98\verb+<file_prefix>.gen+, that may be used as input to the stand alone
99version of the NBO program, gennbo.  \verb+<file_prefix>+ is equal to
100string following the \verb+START+ directive.  The input deck may be edited
101to provide additional options to the NBO calculation, (see the NBO
102user's manual for details.)
103
104\subsection{AIM file}
105\label{sec:AIMfile}
106
107The keyword {\tt aimfile} creates a \verb+.wfn+ file from a given
108eigenvector file (i.e., \verb+.movecs+), geometry and a basis set.
109The \verb+.wfn+ file summarizes the single determinant wavefunction in order to be analyzed
110through a third-party software.
111Among some known analyses are the Bader's approach for atoms in molecules (AIM), the electron
112localization function (ELF), the Fermi hole function and energy density analysis.
113The follow input directive will create the an AIM file \verb+.wfx+ format.
114\begin{verbatim}
115 set prop:nowfx F
116\end{verbatim}
117