1%
2% $Id$
3%
4\label{sec:scfgrad}
5
6
7The input for this directive allows the user to adjust the print control
8for the SCF, UHF, ROHF, MCSCF and MP2 gradients.  The
9form of the directive is as follows:
10
11% RJH removed
12%    [chkpt <integer minutes>]
13%    [restart]
14
15\begin{verbatim}
16  GRADIENTS
17    [print || noprint] ...
18  END
19\end{verbatim}
20
21%The directive contains two keywords, \verb+chkpt+ and \verb+restart+,
22%that are related to the creation of the gradients.  The keyword
23%\verb+chkpt+ allows the user to specify a time interval at which the
24%current values for the forces that make up the gradient are saved, for
25%access by a later calculation.  The time interval is specified in the
26%integer variable \verb+minutes+, and defines the number of minutes of
27%elapsed wall-clock time since the start of the calculation when the
28%gradient is written to the runtime database.
29%RJH: No default chkpt value?  What happens if this is not specified?--fmr.
30
31% \section{CHKPT}
32
33%  This keyword is used to specify a time interval after which a
34%  checkpoint for later restart is created. After \verb+minutes+
35%  minutes of walltime the forces are written to the runtime database.
36
37% \section{RESTART}
38
39%Specifying the keyword \verb+restart+ allows the user to restart a calculation
40%using the gradient from a previous calculation that may have
41%aborted for some reason  (This implies, of course, that the previous
42%calculation employed the keyword \verb+chkpt+ with a value specified for
43%the variable \verb+minutes+, which allowed the calculation to write out the
44%gradient before failing).  The keyword \verb+restart+ allows the partially
45%calculated forces from the previous calculation to be used as the starting
46%point for the new calculation.  If the gradient was not saved previously,
47%however, this keyword has no effect, and the gradients are automatically
48%recalculated from zero.
49
50%  This keyword tells the program that this is a restart of an aborted
51%  gradient calculation. The partially calculated forces are taken from
52%  the database of the previous run. If they are not present, the
53%  keyword is ignored and a complete calculation of the gradients is started.
54
55%  This also works within a geometry optimization. Once a gradient
56%calculation has completed, restart information is automatically
57%deleted
58%so that subsequent gradient
59%  calculations are not treated as restarts.
60%RJH: I don't get the significance of this paragraph.  Elaborate on it?
61%Is it saying that gradient calculations can be saved and restarted even
62%if you are in the middle of a geometry optimization?  But once a
63%gradient is completely calculated, the data that got you there is
64%erased, even if you do have a chkpt directive statement?--fmr.
65
66% \section{PRINT, NOPRINT}
67
68The complementary keyword pair \verb+print+ and \verb+noprint+ allows
69the user some additional control on the information that can be
70included in the print output from the SCF calculation.  Currently,
71only a few items can be explicitly invoked via print control.  These
72are as follows:
73
74%  Currently only some print control is available.
75
76\begin{table}[htbp]
77\begin{center}
78\begin{tabular}{lcc}
79  {\bf Name}       & {\bf Print Level} & {\bf Description} \\
80 ``information''   &       low         & calculation info\\
81 ``geometry''      &      high         & geometry information\\
82 ``basis''         &      high         & basis set(s) used\\
83 ``forces''        &       low         & details of force components\\
84 ``timing''        &     default       & timing for each phase\\
85\end{tabular}
86\end{center}
87\caption{Gradient Print Control Specifications}
88\end{table}
89
90
91