2 * posic.c - precipitation process of silicon carbide in silicon
4 * author: Frank Zirkelbach <hackbard@hackdaworld.org>
10 #define RAND(max) (max*(0.5-(1.0*rand()/RAND_MAX+1)));
12 int main(int argc,char **argv) {
16 int i,j,runs,amount_si;
21 double deltax,deltay,deltaz,distance;
22 double deltax2,deltay2,deltaz2,tmp;
27 printf("simulating %d silicon atoms\n",amount_si);
28 si=malloc(amount_si*sizeof(t_atom));
30 perror("silicon malloc");
33 memset(si,0,amount_si*sizeof(t_atom));
37 printf("placing silicon atoms\n");
38 for(i=0;i<amount_si;i++) {
56 printf("opening the rasmol file\n");
57 fd=open("rasmol.xyz",O_WRONLY);
59 perror("rasmol file open");
63 printf("starting velocity verlet: ");
66 for(runs=0;runs<RUNS;runs++) {
71 * r(t+h) = r(t) + h * dr/dt|t + h^2/2m * F(t)
72 * dr/dt|(t+h) = dr/dt|t + h/2m * (F(t) + F(t+h))
75 for(i=0;i<amount_si;i++) {
76 /* calculation of new positions r(t+h) */
77 si[i].x+=si[i].vx*tau;
78 si[i].y+=si[i].vy*tau;
79 si[i].z+=si[i].vz*tau;
80 si[i].x+=(tau2*si[i].fx/m2);
81 if(si[i].x>LX) si[i].x-=LEN_X;
82 else if(si[i].x<-LX) si[i].x+=LEN_X;
83 si[i].y+=(tau2*si[i].fy/m2);
84 if(si[i].y>LY) si[i].y-=LEN_Y;
85 else if(si[i].y<-LY) si[i].y+=LEN_Y;
86 si[i].z+=(tau2*si[i].fz/m2);
87 if(si[i].z>LZ) si[i].z-=LEN_Z;
88 else if(si[i].z<-LZ) si[i].z+=LEN_Z;
89 /* calculation of velocities v(t+h/2) */
90 si[i].vx+=(tau*si[i].fx/m2);
91 si[i].vy+=(tau*si[i].fy/m2);
92 si[i].vz+=(tau*si[i].fz/m2);
94 for(i=0;i<amount_si;i++) {
95 /* calculation of forces at new positions r(t+h) */
97 deltax=si[i].x-si[j].x;
98 if(deltax>LX) deltax-=LEN_X;
99 else if(-deltax>LX) deltax+=LEN_X;
100 deltax2=deltax*deltax;
101 deltay=si[i].y-si[j].y;
102 if(deltay>LY) deltay-=LEN_Y;
103 else if(-deltay>LY) deltay+=LEN_Y;
104 deltay2=deltay*deltay;
105 deltaz=si[i].z-si[j].z;
106 if(deltaz>LZ) deltaz-=LEN_Z;
107 else if(-deltaz>LZ) deltaz+=LEN_Z;
108 deltaz2=deltaz*deltaz;
109 distance=deltax2+deltay2+deltaz2;
110 if(distance<=R2_CUTOFF) {
111 tmp=1.0/distance; // 1/r^2
129 /* calculation of new velocities v(t+h) */
130 si[i].vx+=(tau*si[i].fx/m2);
131 si[i].vy+=(tau*si[i].fy/m2);
132 si[i].vz+=(tau*si[i].fz/m2);
137 /* print out positions in rasmol format */
138 dprintf(fd,"%d\nTime %f\n",amount_si,time);
139 for(i=0;i<amount_si;i++)
140 dprintf(fd,"Si %f %f %f %f\n",
141 si[i].x,si[i].y,si[i].z,time);