The TIS section

The TIS section defines settings for (PP)TIS and (PP)RETIS simulations.

Example TIS section:
TIS settings
------------
aimless = True
allowmaxlength = False
freq = 0.5
high_accept = True
interface_sour = None
maxlength = 20000
n_jumps = 8
rgen = rgen
rescale_energy = False
seed = 1
shooting_moves = ['sh']
sigma_v = -1
zero_momentum = False

Keywords for the TIS section

The following keywords can be set for the TIS section:

Table 30 Keywords for the TIS section
Keyword Description
aimless Specify if the shooting is aimless or not.
allowmaxlength Specify if the maximum length should be determined randomly.
freq Define how often time reversal moves are performed.
interface_sour Sets the position of SOUR for Web Throwing.
high_accept Set the Stone Skipping version to use.
maxlength Set the maximum length of the paths generated.
n_jumps Set the number of jumps for SS, WT and WF moves.
rgen Set the random number generator to use.
seed Set a seed for the random number generator.
rescale_energy Selects re-scaling of velocities.
shooting_moves Set the MC shooting moves in each ensemble.
interface_cap Set the cap value for subpaths generated by the WF move.
sigma_v Set standard deviations for the random velocity generation
zero_momentum Specify is momentum should be set to zero when shooting.

Keyword aimless

aimless = boolean

Determines if we are to do aimless shooting or not. If this is set to False, then standard deviations for velocity generation can be set by the keyword sigma_v.

Default
The default is aimless = True.

Keyword allowmaxlength

allowmaxlength = boolean

If True, the maximum length for all paths are set to the value given by the keyword maxlength. If False, the maximum length is determined at random based on the length of the current path we are shooting from.

Default
The default is allowmaxlength = False.

Keyword freq

freq = float

This defines how often time reversal moves are performed: E.g. if freq = 0.4 then 40% of the TIS moves are time reversal. Note that if you are running a RETIS simulation, then the percentage of TIS moves will be modified by the percentage of swapping moves, e.g. the percentage of shooting moves will then be given by (1 - swapfreq) \times (1 - freq).

Default
No default, this keyword must be specified.

Keyword interface_sour

interface_sour = float

This defines the position of the SOUR interface for Web Throwing. It HAS to be smaller then the interface defining the ensemble where WT is used. Note that an improper selection of interface_sour will hinder the sampling efficiency.

Default
No default, this keyword must be specified if WT is used.

Keyword high_accept

high_accept = boolean

This select the version of Stone Skipping that is going to be used. Potential High Accept should always been choosen since it is more efficient. Note that the current implementation, due to detailed balance, DOES NOT ALLOW to have multiple shooting methods in the same ensemble.

Default
The default is high_accept = True.

Keyword maxlength

maxlength = integer

This determines the maximum length of the paths generated. Ideally, no paths should be longer than this value. A value too ristrictive can invalidate detailed balance.

Default
No default, this keyword must be specified.

Keyword n_jumps

n_jumps = integer

The number of jumps for Stone Skipping, Wire Fencing and of web for Web Throwing.

Default
No default, this keyword must be specified if Stone Skipping, Wire Fencing or Web Throwing are going to be used.

Keyword rgen

rgen = string

Selection of the random number generator to use. The option allows the use of bias random number generator (mock) or an easy implementation of more advanced random number generators.

Default
The default is rgen = rgen.

Keyword rescale_energy

rescale_energy = float or boolean

If this keyword is set to a number, then the velocities are re-scaled so that the total energy is equal to the given number. This is useful for performing NVE simulations. If the keyword is set to False, then the energies will not be re-scaled.

Default
The default value is rescale_energy = False.

Keyword seed

seed = integer

This integer is a seed for the random number generator used in the TIS algorithm (e.g. when selecting a shooting point).

Default
The default is seed = 0.

Keyword shooting_moves

shooting_moves = list of strings

This list contains the flags that determines the shooting move to be used for each ensemble. Usable moves are ‘sh’ for shooting, ‘ss’ for Stone Skipping, ‘wt’ for Web Throwing and ‘wf’ for Wire Fencing.

Default
The default value is [].

Keyword interface_cap

interface_cap = float

This defines the position of the cap interface for Wire Fencing. It HAS to be larger than the interface defining the ensemble where WF is used. Note that an inproper selection of interface_cap can hinder the sampling efficiency.

Default
No default.

Keyword sigma_v

sigma_v = float

This keyword can be used to set standard deviations for the random velocity generation if the keyword aimless is set to False.

Default
The default value is sigma_v = -1.

Keyword zero_momentum

zero_momentum = boolean

If this keyword is set to True, then the momentum of the system is set to zero after creating random velocities for shooting. If False, this is not done.

Default
The default is zero_momentum = False.