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$DRC group (relevant for RUNTYP=DRC)
This group governs "direct dynamics", following the
dynamical reaction coordinate, which is a classical
trajectory based on quantum chemistry potential energy
surfaces. These may be either ab initio or semi-empirical,
and are computed "on the fly" as the trajectory proceeds.
Because the vibrational period of a normal mode with
frequency 500 wavenumbers is 67 fs, a DRC needs to run for
many steps in order to sample a representative portion of
phase space. Restart data can be found in the job's OUTPUT
file, with important results summarized to the TRAJECT
file. Almost all DRCs break molecular symmetry, so build
your molecule with C1 symmetry in $DATA, or specify NOSYM=1
in $CONTRL. RUNTYP=DRC may not be used with EFP particles.
NSTEP = The number of DRC points to be calculated, not
including the initial point. (default = 1000)
DELTAT = is the time step. (default = 0.1 fs)
TOTIME = total duration of the DRC computed in a previous
job, in fs. The default is the correct value
when initiating a DRC. (default=0.0 fs)
* * *
In general, a DRC can be initiated anywhere,
so $DATA might contain coordinates of the
equilibrium geometry, or a nearby transition
state, or something else. You must also
supply an initial kinetic energy, and the
direction of the initial velocity, for which
there are a number of options:
EKIN = The initial kinetic energy (default = 0.0
kcal/mol)
See also ENM, NVEL, and VIBLVL regarding alternate
ways to specify the initial value.
VEL = an array of velocity components, in Bohr/fs.
When NVEL is false, this is simply the direction
of the velocity vector. Its magnitude will be
automatically adjusted to match the desired
initial
kinetic energy, and it will be projected so that
the translation of the center of mass is removed.
Give in the order vx1, vy1, vz1, vx2, vy2, ...
NVEL = a flag to compute the initial kinetic energy from
the input VEL using the sum of mass*VEL*VEL/2.
This flag is usually selected only for restarts.
(default=.FALSE.)
The next three allow the kinetic energy to be
partitioned over all normal modes. The
coordinates in $DATA are likely to be from
a stationary point! You must also supply $HESS
input, which is the nuclear force constant
matrix at the starting geometry.
VIBLVL = a flag to turn this option on (default=.FALSE.)
VIBENG = an array of energies (in units of multiples of
the hv of each mode) to be imparted along each
normal mode. The default is to assign the zero
point energy only, VIBENG(1)=0.5, 0.5, ..., 0.5
when HESS=MIN, and 0.0, 0.5, ..., 0.5 if HESS=TS.
If given as a negative number, the initial
direction of the velocity vector is along the
reverse direction of the mode. "Reverse" means
the phase of the normal mode is chosen such that
the largest magnitude component is a negative
value. An example might be VIBENG(4)=2.5 to add
two quanta to mode 4, along with zero point
energy in all modes.
RCENG = reaction coordinate energy, in kcal/mol. This is
the initial kinetic energy given to the imaginary
frequency normal mode when HESS=TS. If this is
given as a negative value, the direction of the
velocity vector will be the "reverse direction",
meaning the phase of the normal mode will be
chosen so its largest component is negative.
* * *
The next two pertain to initiating the DRC along
a single normal mode of vibration. No kinetic
energy is assigned to the other modes. You must
also supply $HESS input for the initial geometry.
NNM = The number of the normal mode to which the initial
kinetic energy is given. The absolute value of NNM
must be in the range 1, 2, ..., 3N-6. If NNM is a
positive/negative value, the initial velocity will
lie in the forward/reverse direction of the mode.
"Forward" means the largest normal mode component
is a positive value. (default=0)
ENM = the initial kinetic energy given to mode NNM,
in units of vibrational quanta hv, so the amount
depends on mode NNM's vibrational frequency, v.
If you prefer to impart an arbitrary initial
kinetic energy to mode NNM, specify EKIN instead.
(default = 0.0 quanta)
To summarize, there are 5 ways to initiate a trajectory:
1. VEL vector with NVEL=.TRUE. This is difficult to
specify at your initial point, and so this option
is mainly used when restarting your trajectory.
The restart information is always in this format.
2. VEL vector and EKIN with NVEL=.FALSE. This will
give a desired amount of kinetic energy in the
direction of the velocity vector.
3. VIBLVL and VIBENG and possibly RCENG, to give some
initial kinetic energy to all normal modes.
4. NNM and ENM to give quanta to a single normal mode.
5. NNM and EKIN to give arbitrary kinetic energy to
a single normal mode.
* * *
The most common use of the next two is to analyze
a trajectory with respect to the normal modes of
a minimum energy geometry it travels around.
NMANAL = a flag to select mapping of the mass-weighted
Cartesian DRC coordinates and velocity (conjugate
momentum) in terms of normal modes at a nearby
reference stationary point (which can be either a
minimum or transition state). This reference
geometry could in fact be the same as the initial
point of the DRC, but does not need to be.
If you choose this option, you must supply C0,
HESS2, and $HESS2 input corresponding to the
reference stationary point. (default=.FALSE.)
C0 = an array of the coordinates of the stationary
reference point (the coordinates in $DATA might
well be some other coordinates). Give in the
order x1,y1,z1,x2,y2,... in Angstroms.
* * *
The next options apply to input choices which may
read a $HESS at the initial DRC point, namely NNM
or VIBLVL, or to those that read a $HESS2 at some
reference geometry (NMANAL).
HESS = MIN indicates the hessian supplied for the initial
geometry corresponds to a minimum (default).
= TS indicates the hessian is for a saddle point.
HESS2 = MIN (default) or TS, the same meaning, for the
reference geometry.
These are used to decide if modes 1-6 (minimum) or
modes 2-7 (TS) are to be excluded from the hessian
as the translational and rotational contaminants.
If the initial and reference geometries are the same,
these two hessians will be duplicates of each other.
The next variables can cause termination of a run, if
molecular fragments get too far apart or close together.
NFRGPR = Number of atom pairs whose distance will be
checked. (default is 0)
IFRGPR = Array of the atom pairs. 2 times NFRGPR values.
FRGCUT = Array for a boundary distance (in Bohr) for atom
pairs to end DRC calculations. The run will
stop if any distance exceeds the tolerance, or if
a value is given as a negative number, if the
distance becomes shorter than the absolute value.
In case the trajectory starts outside the bounds
specified, they do not apply until after the
trajectory reaches a point where the criteria
are satisfied, and then goes outside again.
Give NFRGPR values.
* * *
The final variables control the volume of output.
Let F mean the first DRC point found in this run,
and L mean the last DRC point of this run.
NPRTSM = summarize the DRC results every NPRTSM steps,
to the TRAJECT file. (default = 1)
NPRT = 1 Print orbitals at all DRC points
0 Print orbitals at F+L (default)
-1 Never print orbitals
NPUN = 2 Punch all orbitals at all DRC points
1 Punch all orbitals at F+L, and occupied
orbitals at DRC points between
0 Punch all orbitals at F+L only (default)
-1 Never punch orbitals
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generated on 7/7/2017