forked from PTEROSOR/QUESTDB
saving work
This commit is contained in:
parent
d7cd8332a6
commit
19c1a81748
@ -299,7 +299,7 @@ to be extrapolated. This relation is valid in the regime of a sufficiently large
|
||||
correction largely dominates.
|
||||
However, in practice, due to the residual higher-order terms, the coefficient $\alpha^{(m)}$ deviates slightly from unity.
|
||||
|
||||
Using Eq.(\ref{eqx}) the estimated error on the CIPSI energy is calculated as
|
||||
Using Eq.~\eqref{eqx} the estimated error on the CIPSI energy is calculated as
|
||||
\begin{equation}
|
||||
E_{\text{CIPSI}}^{(m)} - E_{\text{FCI}}^{(m)}
|
||||
= \qty(E_\text{var}^{(m)}+E_{\text{rPT2}}^{(m)}) - E_{\text{FCI}}^{(m)}
|
||||
@ -311,11 +311,11 @@ state is given by
|
||||
\Delta E_{\text{FCI}}^{(m)}
|
||||
= \qty[ E_\text{var}^{(m)} + E_{\text{rPT2}} + \qty(\alpha^{(m)}-1) E_{\text{rPT2}} ]
|
||||
- \qty[ E_\text{var}^{(0)} + E_{\text{rPT2}} + \qty(\alpha^{(0)}-1) E_{\text{rPT2}} ]
|
||||
+ O\qty[{E_{\text{rPT2}}^2 }]
|
||||
+ \mathcal{O}\qty[{E_{\text{rPT2}}^2 }],
|
||||
\end{equation}
|
||||
which evidences that the error in $\Delta E_{\text{FCI}}^{(m)}$ can be expressed as $\qty(\alpha^{(m)}-\alpha^{(0)}) E_{\text{rPT2}} + O\qty[{E_{\text{rPT2}}^2}]$.
|
||||
which evidences that the error in $\Delta E_{\text{FCI}}^{(m)}$ can be expressed as $\qty(\alpha^{(m)}-\alpha^{(0)}) E_{\text{rPT2}} + \mathcal{O}\qty[{E_{\text{rPT2}}^2}]$.
|
||||
|
||||
Now, for the largest systems considered here, $\qty|{E_{\text{rPT2}}}|$ can be as large as 2~eV and, thus,
|
||||
Now, for the largest systems considered here, $\abs{E_{\text{rPT2}}}$ can be as large as 2~eV and, thus,
|
||||
the accuracy of the excitation energy estimates strongly depends on our ability to compensate the errors in the calculations.
|
||||
Here, we greatly enhance the compensation of errors by making use of
|
||||
our selection procedure ensuring that the PT2 values of both states
|
||||
@ -325,12 +325,12 @@ E_{\text{rPT2}}^{(0)} \approx E_{\text{rPT2}}^{(m)}$, and
|
||||
by using a common set of state-averaged natural orbitals with equal weights for the ground and excited states.
|
||||
This last feature tends to make the values of $\alpha^{(0)}$ and $\alpha^{(m)}$ very close to each other, such that the error on the energy difference
|
||||
is decreased.
|
||||
In the ideal case where we would be able to fully correlate the CIPSI calculations for the ground- and excited-states, the fluctuations of
|
||||
In the ideal case where we would be able to fully correlate the CIPSI calculations associated with the ground and excited states, the fluctuations of
|
||||
$\Delta E_\text{CIPSI}^{(m)}(n)$ as a function of $n$ would completely vanish and the exact excitation energy would be obtained from the first CIPSI iterations.
|
||||
Quite remarkably, in practice, numerical experience shows that the fluctuations with respect to the extrapolated value $\Delta E_\text{FCI}^{(m)}$ are small,
|
||||
zero-centered, almost independent of $n$ when not too close iteration
|
||||
numbers are considered, and display a Gaussian-like distribution.
|
||||
In addition, the fluctuations are found to be (very weakly) dependent on the iteration number $n$ (see, Fig.\ref{fig2}), so
|
||||
In addition, as stated just above, the fluctuations are found to be (very weakly) dependent on the iteration number $n$ (see Fig.~\ref{fig:histo}), so
|
||||
this dependence will not significantly alter our results and will not be considered here.
|
||||
We thus introduce the following random variable
|
||||
\begin{equation}
|
||||
@ -348,7 +348,7 @@ A natural choice for $\sigma^2(n)$, playing here the role of a variance, is
|
||||
\begin{equation}
|
||||
\sigma^2(n) \propto \qty[E_{\text{rPT2}}^{(m)}(n)]^2 + \qty[E_{\text{rPT2}}^{(0)}(n)]^2,
|
||||
\end{equation}
|
||||
which vanishes in the large-$n$ limit as it should be.
|
||||
which vanishes in the large-$n$ limit as it should.
|
||||
|
||||
%%% FIGURE 2 %%%
|
||||
\begin{figure}
|
||||
@ -357,19 +357,19 @@ which vanishes in the large-$n$ limit as it should be.
|
||||
\caption{Histogram of the random variable $X^{(m)}$ (see, text). About 200 values of the transition energies
|
||||
for the 13 five- and six-membered ring molecules, both for the singlet and triplet transitions and for a number of CIPSI iterations, are used.
|
||||
The number $M$ of iterations kept is chosen according to the statistical test presented in the text.}
|
||||
\label{fig2}
|
||||
\label{fig:histo}
|
||||
\end{figure}
|
||||
|
||||
The histogram of $X^{(m)}$ resulting from the excitation energies
|
||||
obtained at different values of the CIPSI iterations $n$
|
||||
and for the 13 five- and six-membered ring molecules, both for the singlet and triplet transitions,
|
||||
is shown in Fig.\ref{fig2}. To avoid transient effects, only excitation energies at sufficiently large $n$ are retained in the data set.
|
||||
is shown in Fig.~\ref{fig:histo}. To avoid transient effects, only excitation energies at sufficiently large $n$ are retained in the data set.
|
||||
The criterion used to decide from which precise value of $n$ the data should be kept will be presented below. In our application, the total number
|
||||
of values employed to make the histogram is about 200. The dashed line of Fig.\ref{fig2} represents the best Gaussian fit
|
||||
of values employed to make the histogram is about 200. The dashed line of Fig.~\ref{fig:histo} represents the best Gaussian fit
|
||||
(in the sense of least-squares) reproducing the data.
|
||||
As seen, the distribution can be described by the Gaussian probability
|
||||
\begin{equation}
|
||||
P\qty[X^{(m)}] \propto e^{-\frac{{X^{(m)}}^2} {2{\sigma^{*}}^2}}
|
||||
P\qty[X^{(m)}] \propto \exp[-\frac{{X^{(m)}}^2} {2{\sigma^{*}}^2} ]
|
||||
\end{equation}
|
||||
where $\sigma^{*2}$ is some "universal" variance depending only
|
||||
on the way the correlated selection of both states is done, not on the molecule considered in our set.
|
||||
@ -380,7 +380,7 @@ $$\Delta E_\text{FCI}^{(m)} = \frac{ \sum_{n=1}^M \frac{\Delta E_\text{CIPSI}^{
|
||||
$$
|
||||
where $M$ is the number of data kept.
|
||||
Now, regarding the estimate of the error on $\Delta E_\text{FCI}^{(m)}$ some caution is required since, although the distribution is globally Gaussian-like
|
||||
(see Fig.\ref{fig2}) there exists
|
||||
(see Fig.~\ref{fig:histo}) there exists
|
||||
some significant departure from it and we need to take this feature into account.
|
||||
|
||||
More precisely, we search for a confidence interval $\mathcal{I}$ such that the true value of the excitation energy $\Delta E_{\text{FCI}}^{(m)}$ lies within one standard deviation of $\Delta E_\text{CIPSI}^{(m)}$, i.e., $P\qty( \Delta E_{\text{FCI}}^{(m)} \in \qty[ \Delta E_\text{CIPSI}^{(m)} \pm \sigma ] \; \Big| \; \mathcal{G}) = 0.6827$.
|
||||
@ -1238,9 +1238,10 @@ MAE & & 0.22 & 0.16 & 0.22 & 0.11 & 0.12 & 0.05 & 0.04 & 0.02 & 0.20 & 0.22
|
||||
\end{threeparttable}
|
||||
\end{sidewaystable}
|
||||
|
||||
%%% FIGURE 5 %%%
|
||||
\begin{figure}
|
||||
\centering
|
||||
\includegraphics[width=0.9\textwidth]{histograms}
|
||||
\includegraphics[width=0.9\textwidth]{fig5}
|
||||
\caption{Distribution of the error (in eV) in excitation energies (with respect to the TBE/aug-cc-pVTZ values) for various methods for the entire QUEST database considering only closed-shell compounds.
|
||||
Only the ``safe'' TBEs are considered (see Table \ref{tab:TBE}).
|
||||
See Table \ref{tab:stat} for the values of the corresponding statistical quantities.
|
||||
|
Binary file not shown.
Before Width: | Height: | Size: 2.0 MiB After Width: | Height: | Size: 2.0 MiB |
Loading…
Reference in New Issue
Block a user