!       PERFORM THE FREE-FLIGHT AND SCATTER PART WITHIN ONE TIME INTERVAL  
subroutine free_flight_scatterVar()
! common &/ran_var/iso &/scatt_par/emax,de,w(10,3),tau_max(3),max_scatt_mech(3) &/time_1/dt,dtau,tot_time
! &/variables/p(20000,7),ip(20000),energy(20000) &/particle_atr/kx,ky,kz,iv,e &/frequency/freq(10,3)
    use particles
    use scattering
    use simulation
    integer valley,i,j
    real ( kind = 8 ), dimension(DIM) :: Temp_wvk, Temp_pos  ! carrier position and wave vector k 
    integer :: Temp_valley,Temp_use, Temp_ScatMech, CountValley, Temp_nTBin, Temp_nAlBin, nBinComb !, Temp_valley_f 0709
    real ( kind = 8 ) :: Temp_ene, Temp_tau
    real ( kind = 8 ):: timeFreeFlight1,timeFreeFlight2,timeDrift,timeNewFlight, dt_remain, err1
 !     Reset counter for scattering frequency
    do i = 1,num_ScatMech 
        do j = 1,num_Valley 
         ScatMechFreq(i,j) = 0.
        enddo
    enddo
    do i = 1, num_maxCarriers ! num_Carriers 	! loop for all carriers
     if (Par_use(i).eq.1) then
!     Inverse mapping of particle atributes
        do j = 1,DIM !col_len = RCutoff_SiIn
            Temp_wvk(j) = Par_wvk(i,j)
            Temp_pos(j) = Par_pos(i,j)
        enddo
        Temp_tau = Par_tau(i)
        Temp_valley = Par_valley(i)
        Temp_ene = Par_ene(i)        
        Temp_use = Par_use(i)
        Temp_nAlBin = Par_Al(i)
        timeFreeFlight1 = Temp_tau !     Initial free-flight of the carriers
        if(timeFreeFlight1.ge.time_step)then
          timeDrift = time_step 
        else
          timeDrift = timeFreeFlight1
        endif
        call drift(timeDrift,Temp_wvk,Temp_pos,Temp_ene,Temp_valley,Temp_nAlBin,Temp_use) ! Add 08/2013 for Al Content  
        if(Temp_use.eq.0) goto 413       
        if(timeFreeFlight1.gt.time_step) goto 411
     !   Free-flight and scatter part
412     timeFreeFlight2=timeFreeFlight1   
        Temp_nTBin = num_Bins
        do j = 1,num_Bins ! 
          if ((Temp_pos(1).ge.(loc_bin(j)-0.5*BinSize)).and.(Temp_pos(1).lt.(loc_bin(j)+0.5*BinSize))) then
            Temp_nTBin = j
          endif           
        enddo
        nBinComb = CombBin(Temp_nAlBin,Temp_nTBin)
!        if ((Temp_ene.le.MaxE_eV).and.(Temp_ene.gt.0)) then         else            err1 = 1  ! for debugging        endif
        CountValley = Temp_valley
        call TempVar_scatter_carrier(nBinComb,Temp_nAlBin,Temp_wvk,Temp_ene,Temp_valley,Temp_ScatMech)  
        if (Temp_ScatMech.ne.0) then ! phonon counting 0709 
            TempVar_BinScatCount(Temp_nTBin,Temp_ScatMech,CountValley) = TempVar_BinScatCount(Temp_nTBin,Temp_ScatMech,CountValley) + 1 ! Phonon Simulation 11/2012
            AllScatCount(Temp_ScatMech,CountValley) = AllScatCount(Temp_ScatMech,CountValley) + 1      
            BinScatCount(Temp_nTBin,Temp_ScatMech,CountValley) = BinScatCount(Temp_nTBin,Temp_ScatMech,CountValley) + 1
        endif               	
229     call random_number(harvest = RandomNum)
        if(RandomNum.le.1e-6) goto 229
        timeNewFlight=-(log(RandomNum))*TempVar_tau_max(nBinComb,Temp_valley)
        dt_remain = time_step - timeFreeFlight2	! remaining time to scatter in dt-interval
        if(timeNewFlight.le.dt_remain)then
          timeDrift = timeNewFlight
        else
          timeDrift = dt_remain
        endif  !       if ((Temp_ene.le.MaxE_eV).and.(Temp_ene.gt.0)) then    else    err1 = 1  ! for debugging        endif
        call drift(timeDrift,Temp_wvk,Temp_pos,Temp_ene,Temp_valley,Temp_nAlBin,Temp_use) ! Add 08/2013 for Al Content  
        if(Temp_use.eq.0) goto 413 ! if not use... 
        timeFreeFlight2 = timeFreeFlight2 + timeNewFlight !     Update times
        timeFreeFlight1 = timeFreeFlight2
        if(timeFreeFlight1.lt.time_step) goto 412   
411     timeFreeFlight1 = timeFreeFlight1 - time_step 
        Temp_tau = timeFreeFlight1
        do j = 1,DIM !col_len = RCutoff_SiIn !     Map particle atributes
            Par_wvk(i,j) = Temp_wvk(j)
            Par_pos(i,j) = Temp_pos(j)
        enddo 
        Par_tau(i) = Temp_tau
        Par_valley(i) = Temp_valley
        Par_Al(i) = Temp_nAlBin
        Par_ene(i) = Temp_ene  !       if ((Par_ene(i).le.MaxE_eV).and.(Par_ene(i).gt.0)) then         else            err1 = 1  ! for debugging        endif
413     Par_use(i) = Temp_use	             
     endif
    enddo
    return	
end