Monte Carlo Simulation Opcodes

The opcodes in this section are linked below:

MCLO — Monte CarLO simulation

MCLO — Monte CarLO simulation

Carry out classical internal coordinate Metropolis Monte Carlo simulation for sampling of phase space. Use MDYN, MCSD or MCLO commands to identify internal degrees of freedom to be varied. RCA4 commands are allowed, but a low acceptance ratio can be expected unless IMPS is being used.

The MDSA command provides control over the extent of output in MCLO as well as MDYN procedures.

arg1

Extent of listing

0

No listing.

1

Listing to .mmo file.

arg2

Number of internal coordinates varied at each MC step

0

Each MDYN, MCSD or MCLO command corresponds to one internal coordinate degree of freedom. Each molecule moved by a MOLS command generates one (if only translation or only rotation is being done) or two (if both translation and rotation limits are given) internal coordinate degrees of freedom.
 

This argument is now overridden by args 1 and 2 of the MCNV command. In addition, be aware that MCLO may dynamically override any user specification by using a built-in dynamic method of specifying limits on degrees of freedom varied. The adaptive mechanism may be turned off with DEBG 103.

arg3

Number of MC steps in simulation

>0

Perform this number of steps.

<0

Perform 100,000 times |arg1| steps. This facilitates specifying a large number of steps. (Note that prior to MacroModel 6.5, the multiplier was 100.)

0

Note: Not a valid argument.

arg4

MC restart frequency
 

Every arg4 steps, the original starting geometry is retrieved and the simulation is continued with it.

arg5

Desired MC acceptance ratio
 

Desired ratio of steps which find an acceptable structure to total steps taken. Limits given in MDYN, MCSD or MCLO commands are adjusted to obtain desired acceptance ratio.

0

Use MDYN, MCSD or MCLO values without adjustment.

arg7

Temperature (K)
 

Must be greater than zero.