$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 ========================================================== ===========================================================

generated on 7/7/2017