How to distribute molecules to states using C++

[dilatoryyang]

I don't know how to distribute large amount of molecules(say a million) to many ro-vibrational states(say 100 states), according to the relative population of these states. As is very important when I want to simulate numerically the classical trajectory of these molecules in a spatially inhomogeneous electric field.

 

[alxm]

Doesn't sound very hard. If you have the relative populations, e.g. say 50%, 25%, 15%, 10% (four states) then you could, for instance: Pick a random number between 0 and 1 (which is what most random functions return) if it's 0-.5 assign state 1, if it's 0.5-0.75 assign state 2, 0.75-0.90 assign state 3 and 0.9-1 assign state 4.

 

[quicknote]

I would recommend using a Monte Carlo method to distribute molecules to states in C++. This method involves randomly assigning molecules to states based on their relative population. This can be achieved by generating a random number for each molecule and comparing it to the cumulative distribution function of the states. The molecule will then be assigned to the state corresponding to the random number.

Furthermore, to distribute a large number of molecules, you can use a loop in your code to repeat the Monte Carlo method multiple times. This will ensure that all the molecules are distributed to the states according to their relative population.

Additionally, it is important to consider the efficiency of your code when dealing with a large number of molecules and states. You can optimize your code by using data structures such as arrays or vectors to store the states and their relative populations, and using parallel processing techniques to speed up the distribution process.

Overall, using a Monte Carlo method in C++ is a reliable and efficient way to distribute molecules to states according to their relative population, which is crucial for accurately simulating the classical trajectory of molecules in an electric field.