【正文】 cc =2, find the velocity of secondary electron if () then stemp=temper(ip) else if () then stemp=gtemp else if () then stemp=* end if theta=2.*PI*rand_gen() random=rand_gen() do while () random=rand_gen() end do vel_trm=dsqrt(e*stemp/mass(ip)) svr = vel_trm*dsqrt(*log(random)) svx = svr*dcos(theta) svy = svr*dsin(theta) random=rand_gen() do while () random=rand_gen() end do svz = vel_trm*dsqrt(*log(random)) * *sin(*PI*rand_gen())cc********************************************************///cc find the maxwell distribution functionc vel=sqrt(svx*svx+svy*svy+svz*svz) k=int(vel/vel_trm/)c df_maxw(ip,k)=df_maxw(ip,k)+cc********************************************************///cc if asymetric reactor, spherical coordinates, find the velocitycc in (theta,phi,r), vx is vth, vy is vph, vz is vr if () then tvx=svx tvy=svy tvz=svz phi_sph(ip,np)=*PI*rand_gen() the_sph(ip,np)=PI*rand_gen() cosphi=dcos(phi_sph(ip,np)) sinphi=dsin(phi_sph(ip,np)) costhe=dcos(the_sph(ip,np)) sinthe=dsin(the_sph(ip,np)) svx= tvx*costhe*cosphi+tvy*costhe*sinphitvz*sinthe svy=tvx*sinphi+tvy*cosphi svz= tvx*sinthe*cosphi+tvy*sinthe*sinphi+tvz*costhe end ifcc********************************************************/// return endcc**********************************************************\\\cc end of MAXWVEL2) Inelastic collisionc) Excitationi. The main formula () ()Where Eth is the threshold energy of the inelastic collision, excitation in this case . Taking into consideration that M+m≈M and g≈v we obtain ( ) ()Where E=mv2/2 is the electron energy before collision. The excitation process is treated as if it were an elastic collision with pre_collision velocities and V. The post_collision velocities are given by Eqs.()() in which all v’s are replaced by . ii.d) Ionization(electron_A)Where A denotes the neutral particle with a mass , which can be assumed equal to that of the ion M .The process is represented as ()Where A+ denotes an ion,e1 is the incident electron , e2 is the ejected electron , and the symbols in the parentheses denote the velocities .The energy balance equation is ()Where Eth is the threshold energy of the ionization . Because of the large ion_to_electron mass ratio ,we can assume that the momentum of the incident electron is much lower than the momentum of the neutral particle,. the incident electron removes an electron from the neutral ,and the neutral bees an ion,continuing on its trajectron undisturbed . On one hand ,this assumption means that the created ion takes the velocity and direction of the neutral particle before collision ,. V’=V .On the other hand , the energy balance can be rewritten ()The left_hand side is known as the excess energyΔE after ionization and we need to find an algorithm how to divide it into the scattered and ejected electrons. In general, when there is no published work on the division of the excess energy , it is divided randomly into two () ()For the electron_Ar ionzation ,however,we use the expression for sampling the Eej by a random number R,()Where Einc =mv2/2 is the energy of the incident electron. The units of α0 andα1 are electronvolts .Once the excess energy is divided, v’ is calculated from Eq.() () ()The post_collision velocity of the scattered electron v’ is obtained by Eq() in which v is replaced by .The pre_collision velocity for the ejected electron , which does not exist in reality, is assumed ()and the post_collision velocity is obtained again from Eq.() by replacing v with and v’ with v’ej . For many types of collision no data on differential cross_section is assumed not to depend to the deflection angle x .The total cross_section calculated from Eq.()gives σT=4πσ（g）.Therefore , the probabilityDefined by ()bees sinxdxdφ/ means that the post_collision velocities take random direction. The scattering with this property is called there are no sufficient data for the differential cross_sections of electron_CF4 and electron_N2 collisions we assume that the scattering is isotropic .The approximation of the interaction potential with the screened Coulomb potential made for collisions with atomic Ar is not valid for molecular case of isotropic scattering the deflection angle , which is in the interval [0, π],is randomly sampled by () The angle φ is randomly sampled from () and the post_collision velocities for electron_CF4 and electron_N2 elastic collisions can be found from Eqs.()_().Similar to electron_Ar elastic collisions,these equations can be somewhat simplified by use of M+m≈M and g≈v. Electron_CF4 and electron_N2 inelastic collisions are treated similar to electron_Ar inelastic collisions,taking into account the isotropic scattering after case of ionization,the excess energy is divided by a random number using Eqs .() and () between the scattered and ejected electron .In case of attachment the incident electron is removed from the calculation and the created negative ion takes the velocity and direction of the neutral particle before the collision.2. lon_neutral collisions1) Cross_section dataa) Collisions of Ar+ with neutralsi. Ar+_Ar elastic isotropic sc。ii. subroutine maxwvelcc*********************************************************cccc SUBROUTINE MAXWVEL calculate maxwell velocitycc ip indicate the species iscc np is the present number of the particle i, . vx(is,i)cc*****************************************************