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72 lines
2.8 KiB
TeX
72 lines
2.8 KiB
TeX
% $Id$
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\label{sec:hess}
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This section relates to the computation of analytic hessians which
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are available for open and closed shell SCF, except ROHF and for closed shell
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DFT. Analytic hessians are not currently available for SCF or DFT
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calculations relativistic all-electron methodologies or for charge fitting with DFT. The current
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algorithm is fully in-core and does not use symmetry. This will be
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changed in the next release.
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There is no required input for the Hessian module. This module only
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impacts the hessian calculation. For options for calculating the
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frequencies, please see Section \ref{sec:vib}, the Vibrational module.
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\section{Hessian Module Input}
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All input for the Hessian Module is optional since the default
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definitions are usually correct for most purposes.
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The generic module input begins with \verb+hessian+
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and has the form:
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\begin{verbatim}
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hessian
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thresh <real tol default 1d-6>
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print ...
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profile
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end
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\end{verbatim}
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\subsection{Defining the wavefunction threshold}
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You may modify the default threshold for the wavefunction. This keyword
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is identical to THRESH in the SCF, Section \ref{sec:thresh}, and the
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CONVERGENCE gradient in the DFT, Section \ref{sec:dftconv}. The usual
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defaults for the convergence of the wavefunction for single point and
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gradient calculations is generally not tight enough for analytic hessians.
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Therefore, the hessian, by default, tightens these up to 1d-6 and runs
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an additional energy point if needed. If,
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during an analytic hessian calculation, you encounter an error:
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\begin{verbatim}
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cphf_solve:the available MOs do not satisfy the SCF equations
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\end{verbatim}
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the convergence criteria of the wavefunction generally needs to be
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tightened.
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\subsection{Profile}
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The PROFILE keyword provides additional information concerning the
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computation times of
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different sections of the hessian code. Summary information is
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given about the maximum, minimum and average times that a particular
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section of the code took to complete. This is normally only useful
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for developers.
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\subsection{Print Control}
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Known controllable print options are:
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\begin{table}[h]
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\begin{center}
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\begin{tabular}{lcc}
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{\bf Name} & {\bf Print Level} & {\bf Description} \\
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``hess\_follow'' & high & more information about where the calculation is \\
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``cphf\_cont'' & debug & detailed CPHF information \\
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``nucdd\_cont'' & debug & detailed nuclear contribution information \\
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``onedd\_cont'' & debug & detailed one electron contribution information \\
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``twodd\_cont'' & debug & detailed two electron contribution information \\
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``fock\_xc'' & debug & detailed XC information during the fock builds \\
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\end{tabular}
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\end{center}
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\caption{Hessian Print Control Specifications}
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\end{table}
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