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Time correlation functions: trtcf.f

This utility computes some time correlation functions. For a molecular vector $\vec{n}(t)$, the time correlation function can be determined as:


\begin{displaymath}
c(t) = \frac{\langle\vec{n}(t_0)\cdot\vec{n}(t_0+t)\rangle}
{\langle\vec{n}(t_0)^2\rangle}
\end{displaymath} (15)

where averaging is taken over all molecules of the given type and all acceptable initial times $t_0$: $t_{beg} \le t_0 \le t_{end}-t$, where $t_{beg}$ and $t_{end}$ are initial and final time of a continuous part of the whole trajectory respectively. A trajectory is regarded as continuous if each next configuration differs from the previous by no more than parameter BREAKM defined in the trajectory part (TRAJ) of the input file.

The program can compute the following time correlation functions:

The second Legendre polynomial TCF is defined as:


\begin{displaymath}
c(t) = \frac{\langle L_2(\vec{n}(t_0)\cdot\vec{n}(t_0+t))\rangle}
{\langle L_2(\vec{n}(t_0)^2)\rangle}
\end{displaymath} (16)

where $L_2(x) = 0.5(3\cos^2 x -1)$

Compilation:

f77 -O3 -o trtcf trtcf.f tranal_base.f

Note that compilation of trtcf.f requires, in addition to the common header file tranal.h, another header file trtcf.h, which may need to be edited in order to set array borders matching the studied system

Input parameters for this utility follow after the trajectory parameters in the NAMELIST block TCF:

 $TCF
 parameter=value(s),
 ...
 $END

The following parameters are used:


next up previous contents
Next: About this document ... Up: Tranal utility Previous: Residence time calculation: restime.f   Contents
Alexander Lyubartsev 2015-02-06