TFUNC

This section specifies the target temperature by using the time step and the temperature of the last step, allowing for simple region-wise simulated annealing (heating/cooling) controls. When the absolute difference between target and actual temperature is larger than TEMP_TOL value, the atomic velocities in this region are rescaled to match the target temperature. However, note that the actual temperature is subject to thermostat coupling as well and a small restrictive TEMP_TOL together with a rapidly varying target temperature function leaves little time for the system to adjust itself, possibly showing unphysical relaxation behaviors. Further notes about temperature. A functional form is specified. Mathematical Operators recognized are +, -, *, /, ^ or alternatively **, whereas symbols for brackets must be (). The function parser recognizes the Fortran 90 intrinsic functions abs, min, max, exp, log10, log, sqrt, sinh, cosh, tanh, sin, cos, tan, asin, acos, atan2, atan, erf, erfc. Parsing for intrinsic functions is not case sensitive. [Edit on GitHub]

Keywords

• FUNCTION

• PARAMETERS

• UNITS

• VALUES

Keyword descriptions

FUNCTION: string

Usage: FUNCTION AT+(1-A)B(2/(1+EXP(-0.001S))-1)

Specifies the functional form of the temperature in Kelvin in mathematical notation. Two variables are available with one denoted S for the integer time step and another denoted T for the temperature of the last step in Kelvin respectively. When DEFINE_REGION%TEMPERATURE is not explicitly set, the function will be evaluated at S set in MD%STEP_START_VAL and T = 0.0 to initialize the velocities of atoms in the region. [Edit on GitHub]

PARAMETERS: string[ ]

Keyword can be repeated.

Usage: PARAMETERS A B

Defines the parameters of the functional form [Edit on GitHub]

UNITS: string[ ]

Keyword can be repeated.

Usage: UNITS

Optionally, allows to define valid CP2K unit strings for each parameter value. It is assumed that the corresponding parameter value is specified in this unit. [Edit on GitHub]

VALUES: real[ ] = [internal_cp2k]

Keyword can be repeated.

Usage: VALUES 0.75 3.00E+2

Defines the values of the parameter of the functional form [Edit on GitHub]