Simulated Annealing Dialog
In this dialog you can see or define parameters for Simulated annealing procedure.
In the next lines the actual equivalence with FullProf parameters is shown in dark red.
Algorithm [NALGOR]
Select the type of algorithm to be applied. The options are:
Corana algorithm
There are two different possibilities about the initial steps mode. One is using then whole interval as initial step for all parameters and then adapt progressively their values in order to maintain an approximate rate of accepted configurations between two pre-set values (40% and 60% in our case).
Second, the initial steps are given by user in the BOX / Restraints button on Main Window of EdPCR program.
Conventional algorithm
Conventional algorithm using the fixed steps as given in BOX/Restraints button on Main Window of EdPCR program.
Initial Configuration [INITCONF]
You can choose as initial state a totally random configuration or one given by the values of the respective parameters in the PCR file. This last option is useful when one tries to optimise an already good starting configuration, by controlling the box limits and the steps.
Starting Temperature [T_INI]
Starting temperature in the Simulated Annealing procedure. Arbitrary value, the user should experiment with different values for each problem. A good starting point is a temperature for which the percentage of accepted configurations in the first Montecarlo cycle is of the order of 80-90%.
Cooling rate [ANNEAL]
Value of the constant needed for reducing the temperature for the next Montecarlo cycle. Normally 0.9 is a good value.
Max. number of tested temperature [NUMTEMPS]
Maximum number of temperatures. The program stops after running the algorithm for NUMTEMPS temperatures irrespective of the convergence criterion.
Number of Montecarlo cycles per temperature [NCYCLM]
Number of Montecarlo cycles per temperature. A Montecarlo cycle corresponds to the change of all the free parameters one by one. NCYCLM must be at least 10 to 20 (or more!) times the number of free parameters.
Number of Montecarlo cycles to be excluded from average calculations [NUMTHCYC]
Number of Montecarlo cycles to be excluded from the calculation of averages. This is only useful for non-structural work. Normally 0
Number of select best solution [NSOLU]
Number of solutions to be stored. Due to the nature of the Simulated Annealing algorithm this number should be fixed to 1.
Number of reflections to be used [NREFLEX]
The program uses the first NREFLEX reflections of the file CODFILn.hkl or CODFIL.int
Lower admissible average step for convergence [ACCEPT]
The meaning of ACCEPT is the value of the lowest admissible average
step, i.e. the program stops if Step
≤ ACCEPT.
This holds for the Corana algorithm, when the conventional algorithm is
selected then ACCEPT is the lowest percentage of accepted configurations to
consider the algorithm has converged.
Scale factor calculated automatically [NSCALEF]
If active the checkbox then the scale factor used in the program is obtained from the relation:
Allow interchange of atoms [ISWAP]
If active this option then allow interchange of atoms in the Simulated Annealing algorithm and define the number of Montercalo cycles between interchange pairs of atoms is done. The new configurations are accepted only if the cost function is reduced.
For magnetic structures this flag has to be fixed to zero.
Number of coefficients to be switched between real or pure imaginary in magnetic structure determination [MCOMPL]
(Yellow background indicate that the user need use the spinners in order to active the procedure in correct form)
Number of coefficients to be switched between real or pure imaginary
in magnetic structure determination when the irreducible representations of the
propagation vector group are used.
Activating the respective checkbox means that coefficients will be switched between real and pure imaginary or viceversa.