# 10.7.2 Additional Job Control and Examples

AIMD_INIT_VELOC
Specifies the method for selecting initial nuclear velocities.
TYPE:
STRING
DEFAULT:
None
OPTIONS:
THERMAL Random sampling of nuclear velocities from a Maxwell-Boltzmann distribution. The user must specify the temperature in Kelvin via the $rem variable AIMD_TEMP. ZPE Choose velocities in order to put zero-point vibrational energy into each normal mode, with random signs. This option requires that a frequency job to be run beforehand. QUASICLASSICAL Puts vibrational energy into each normal mode. In contrast to the ZPE option, here the vibrational energies are sampled from a Boltzmann distribution at the desired simulation temperature. This also triggers several other options, as described below. RECOMMENDATION: This variable need only be specified in the event that velocities are not specified explicitly in a$velocity section.

AIMD_MOMENTS
Requests that multipole moments be output at each time step.
TYPE:
INTEGER
DEFAULT:
0 Do not output multipole moments.
OPTIONS:
$n$ Output the first $n$ multipole moments.
RECOMMENDATION:
None

AIMD_TEMP
Specifies a temperature (in Kelvin) for Maxwell-Boltzmann velocity sampling.
TYPE:
INTEGER
DEFAULT:
None
OPTIONS:
User-specified number of Kelvin.
RECOMMENDATION:
This variable is only useful in conjunction with AIMD_INIT_VELOC = THERMAL. Note that the simulations are run at constant energy, rather than constant temperature, so the mean nuclear kinetic energy will fluctuate in the course of the simulation.

DEUTERATE
Requests that all hydrogen atoms be replaces with deuterium.
TYPE:
LOGICAL
DEFAULT:
FALSE Do not replace hydrogens.
OPTIONS:
TRUE Replace hydrogens with deuterium.
RECOMMENDATION:
Replacing hydrogen atoms reduces the fastest vibrational frequencies by a factor of 1.4, which allow for a larger fictitious mass and time step in ELMD calculations. There is no reason to replace hydrogens in BOMD calculations.

Example 10.22  Simulating thermal fluctuations of the water dimer at 298 K.

$molecule 0 1 O 1.386977 0.011218 0.109098 H 1.748442 0.720970 -0.431026 H 1.741280 -0.793653 -0.281811 O -1.511955 -0.009629 -0.120521 H -0.558095 0.008225 0.047352 H -1.910308 0.077777 0.749067$end

$rem JOBTYPE aimd AIMD_METHOD bomd METHOD b3lyp BASIS 6-31g* TIME_STEP 20 (20 a.u. = 0.48 fs) AIMD_STEPS 1000 AIMD_INIT_VELOC thermal AIMD_TEMP 298 FOCK_EXTRAP_ORDER 6 request Fock matrix extrapolation FOCK_EXTRAP_POINTS 12$end


Example 10.23  Propagating $\rm F^{-}(H_{2}O)_{4}$ on its first excited-state potential energy surface, calculated at the CIS level.

$comment Note, only a few time steps are taken, a more appropriate number would be: AIMD_STEPS 827 500 fs$end

$molecule -1 1 O -1.969902 -1.946636 0.714962 H -2.155172 -1.153127 1.216596 H -1.018352 -1.980061 0.682456 O -1.974264 0.720358 1.942703 H -2.153919 1.222737 1.148346 H -1.023012 0.684200 1.980531 O -1.962151 1.947857 -0.723321 H -2.143937 1.154349 -1.226245 H -1.010860 1.980414 -0.682958 O -1.957618 -0.718815 -1.950659 H -2.145835 -1.221322 -1.158379 H -1.005985 -0.682951 -1.978284 F 1.431477 0.000499 0.010220$end

$rem JOBTYPE aimd AIMD_METHOD bomd METHOD hf BASIS 6-31+G* ECP SRLC PURECART 1111 CIS_N_ROOTS 3 CIS_TRIPLETS false CIS_STATE_DERIV 1 propagate on first excited state AIMD_INIT_VELOC thermal AIMD_TEMP 150 TIME_STEP 25 AIMD_STEPS 10$end


Example 10.24  Simulating vibrations of the NaCl molecule using ELMD.

$molecule 0 1 Na 0.000000 0.000000 -1.742298 Cl 0.000000 0.000000 0.761479$end

$rem JOBTYPE freq METHOD b3lyp ECP fit-sbkjc$end

@@@

$molecule read$end

$rem JOBTYPE aimd METHOD b3lyp ECP fit-sbkjc TIME_STEP 14 AIMD_STEPS 500 AIMD_METHOD curvy AIMD_FICT_MASS 360 AIMD_INIT_VELOC zpe$end