Gaussian 03 Online ManualLast update: 2 October 2006 | |

## BOMDThis
keyword requests a classical trajectory calculation [177,178,179,180]
using a Born-Oppenheimer molecular dynamics model (first described in [181,182];
see [403] for an extended review article). The
implementation in The selection of the initial conditions using quasi-classical fixed normal mode sampling and the final product analysis are carried out in the same manner as in the classical trajectory program VENUS [404]. Alternatively, initial Cartesian coordinates and velocities may be read in. Note that the
## REQUIRED INPUTAll If When
the number of dissociation paths is greater than zero, the full
The input line(s) following
Stopping
criteria are specified next when the Minimum distance between the centers of mass for any pair of fragments > *R1*(18)Minimum distance between atoms located in different fragments > *R2*(20)Maximum distance between the center of mass and any atom in the same fragment < *R3*(0)The maximum distance between any pair of atoms in the same fragment < *R4*(0)Interfragment gradient < *G5*(10^{-6})If *ITest*=1, distance between atoms*IAtom*and*JAtom*>*R6*(0)*Otherwise, distance between atoms**IAtom*and*JAtom*<*R6*(0)
All distances are specified in Bohr, and the
units of the gradient Parameters for simulated
annealing/fragmentation follow the stopping criteria in the input stream when
the *Estart*is the desired initial kinetic energy (Hartrees).*DelE*is the energy gain/loss in Hartrees.*SBeta*is the Fermi-Dirac inverse temperature (1/Hartrees).*Ef*is the Fermi energy (wavenumbers): all modes corresponding to a frequency in wavenumbers below*Ef*will be enhanced, whole those above*Ef*will be reduced. The reverse will happen if*SBeta*is negative.*DPert*is the size of the random perturbation.*IFlag*determines the algorithm for applying an energy perturbation for simulated annealing (i.e., adding/removing energy from the eigenmodes). It has the following possible values:**0**(weigh each eigencomponent according to its frequency),**1**(add DelE in a random fashion),**2**(combination of 0 and 1),**00**(if near a transition state, add all energy along that mode), and**10**(ignore any nearby transition state).
The
next part of the input specifies how much energy is in each normal mode when the
Next, the
initial velocity for each atom is read if the Finally, Morse parameter data can be specified for each diatomic
product. The Morse parameter data is used to determine the vibrational excitation
of diatomic fragments using the EBK quantization rules. It consists of the atomic
symbols for the two atoms, the bond length between them (
Only one of
You may also specify alternative
isotopes for All semi-empirical, SCF, CASSCF, CIS, MP2 and DFT methods. The
following sample Stopping
criteria are also specified in this example job. The trajectory will be stopped
if the distance between the centers of mass of H The initial kinetic energy along the transition vector is 5.145 kcal/mol,
in the direction of the products (the forward direction is characterized
by an increase in the larger C-H distance). The Morse parameters for H # HF/3-21G BOMD(Phase=(1,3),RTemp=300,NSample=1,ReadStop) Geom=Crowd HF/3-21G dissociation of H2CO --> H2 + CO 0 1 C O 1 r1 H 1 r2 2 a H 1 r3 3 b 2 180. r1 1.15275608 r2 1.74415774 r3 1.09413376 a 114.81897892 b 49.08562961 1 1 1 2 2 13.0 11.0 1.3 2.5 0.0000005 1 1 3 12.8 1 5.145 C O -112.09329898 1.12895435 0.49458169 2.24078955 H H -1.12295984 0.73482237 0.19500473 1.94603924 Note that all six stopping criteria are used here only for illustrative purposes. In most cases, one or two stopping criteria are sufficient. At the beginning
of a TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ-TRJ ------------------------------------------------------------------- INPUT DATA FOR L118 ------------------------------------------------------------------- General parameters: Max. points for each Traj. = 100 Total Number of Trajectories = 1 Random Number Generator Seed = 398465 Trajectory Step Size = 0.250 sqrt(amu)*bohr Sampling parameters: Vib Energy Sampling Option = Thermal sampling Vib Sampling Temperature = 300.0 K Sampling direction = Forward Rot Energy Sampling Option = Thermal distribution (symmetric top) Rot Sampling Temperature = 300.0 K Start point scaling criteria = 1.000D-05 Hartree ... Reaction Path 1 **************** Fragment 1 center 1 ( C ) 2 ( O ) Fragment 2 center 3 ( H ) 4 ( H ) Termination criteria: The CM distances are larger than 13.000 bohr The min atomic distances among fragments are larger than 11.0 bohr The max atomic and CM distances in frags are shorter than 1.3 bohr The max atomic distances in fragments are short than 2.500 bohr The change of gradient along CM is less than 5.00D-07 Hartree/bohr Distance between atom center 1 ( C ) and 3 ( H ) is GE 12.800 bohr Morse parameters for diatomic fragments: E0 Re De Be C O -112.0932990 1.1289544 0.4945817 2.2407896 H H -1.1229598 0.7348224 0.1950047 1.9460392 --------------------------------------------------------------------- The initial kinetic energies for the normal modes appear at the beginning of each trajectory step: ------------------------------------------------------- Thermal Sampling of Vibrational Modes Mode Wavenumber Vib. quant.# Energy (kcal/mol) ------------------------------------------------------- 1 -2212.761 5.14500 2 837.330 0 1.19702 3 1113.182 0 1.59137 4 1392.476 0 1.99064 5 2026.859 0 2.89754 6 3168.689 0 4.52987 ------------------------------------------------------- After the trajectory computation is complete, summary information is displayed in the output: Trajectory summary for trajectory 1 Energy/gradient evaluations 76 Hessian evaluations 76 Trajectory summary Time (fs) Kinetic (au) Potent (au) Delta E (au) Delta A (h-bar) 0.000000 0.0214192 -113.0388912 0.0000000 0.0000000000000000 1.169296 0.0293490 -113.0468302 -0.0000091 0.0000000000053006 2.161873 0.0407383 -113.0582248 -0.0000144 0.0000000000045404 ... The information is
given for each time step in the trajectory. In addition, the output includes geometrical
parameters for the atoms in each fragment, the distances between fragments, and
the relative mass-weighted velocities for each fragments and between fragments,
all reported at each time step. You can also use |