Fortran 卢瑟福散射实验误差

我对Fortran非常陌生，必须模拟卢瑟福散射实验来完成作业。在代码中，假设有一个金核位于中心（x，y）=（0,0）。我试图根据Colomb定律求出α粒子的加速度、速度和距离。r_lim是一个边界条件，当粒子通过时，循环将成功停止。如果我还能解释什么，请告诉我

PROGRAM rutherford_scatter

IMPLICIT NONE

TYPE particle

REAL:: x,y

END TYPE particle

TYPE(particle):: r_alpha, v_alpha, a_alpha
REAL:: x_0,y_0, v_0, q_gold, q_alpha, k_e, m_alpha, c, c_frac, time_step, r_lim
LOGICAL :: check = .FALSE.

k_e = 1.0
c = 137.053999
time_step = 1.0 *10.0**(-5.0)
q_alpha = 2.0
q_gold = 79.0
m_alpha = 7294.3

WRITE (*,*) 'Enter initial value for x distance.'
READ (*,*) x_0
y_0 = -0.005

WRITE (*,*) 'Enter initial value for velocity (fraction of speed of light).'
READ (*,*) c_frac
v_0 = c_frac * c

r_alpha%x = x_0
r_alpha%y = y_0

r_lim = 1.1 * SQRT(r_alpha%x**2+r_alpha%y**2)


v_alpha%x =  0
v_alpha%y = ABS(v_0)

OPEN (11, FILE = 'assign_11.out')
DO WHILE (check)
    a_alpha = acceleration(k_e, m_alpha, q_gold, q_alpha, r_alpha)
    v_alpha = velocity (v_alpha, a_alpha)
r_alpha = distance (r_alpha, v_alpha)
    WRITE (11,*) r_alpha
    IF (r_alpha%x .GT. r_lim .OR. r_alpha%y .GT. r_lim) THEN
        check =.TRUE.
    END IF
END DO
CLOSE(11)


CONTAINS

TYPE (particle) FUNCTION acceleration (k_e, m_alpha, q_gold, q_alpha,r_alpha)
TYPE (particle), INTENT(IN):: r_alpha
REAL, INTENT (IN)::k_e, m_alpha, q_gold, q_alpha
acceleration%x = (k_e/m_alpha) * ((q_gold * q_alpha)/(ABS(r_alpha%x))**2 )* (r_alpha%x/SQRT(r_alpha%x**2+r_alpha%y**2))
acceleration%y = (k_e/m_alpha) * ((q_gold * q_alpha)/(ABS(r_alpha%y))**2 )*(r_alpha%y/SQRT(r_alpha%x**2+r_alpha%y**2))
END FUNCTION

TYPE (particle) FUNCTION velocity (v_alpha, a_alpha)

TYPE (particle), INTENT (IN):: a_alpha, v_alpha

velocity%x = v_alpha%x + a_alpha%x*time_step
velocity%y = v_alpha%y + a_alpha%y* time_step
END FUNCTION

TYPE(particle) FUNCTION distance (r_alpha, v_alpha)
TYPE (particle), INTENT (IN):: r_alpha, v_alpha

distance%x = r_alpha%x + v_alpha%x * time_step
distance%y = r_alpha%y + v_alpha%y * time_step
END FUNCTION

END PROGRAM rutherford_scatter 

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我们不是你身体问题的专家。请谈谈你的计划的细节，并解释到底发生了什么。如何编译？你提供了哪些信息？程序打印什么？请尝试：执行时（.not.check）