force_flag = 0;

  // foriginal[0] = - x dot f = "potential" for added force

  // foriginal[123] = force on atoms before extra force added

  for (int i = 0; i < nlocal; i++)

    if (mask[i] & groupbit) {

      foriginal[0] -= xvalue*x[i][0] + yvalue*x[i][1] + zvalue[i][2];

      foriginal[0] -= xvalue*x[i][0] + yvalue*x[i][1] + zvalue*x[i][2];

      foriginal[1] += f[i][0];

      foriginal[2] += f[i][1];

      foriginal[3] += f[i][2];