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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@15547 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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sjplimp
2016-09-06 21:55:39 +00:00
parent f9c106897f
commit 56945a56aa
2 changed files with 122 additions and 64 deletions
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71
src/group.cpp
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@ -29,6 +29,7 @@
#include "input.h"
#include "variable.h"
#include "dump.h"
#include "math_extra.h"
#include "memory.h"
#include "error.h"
@ -37,6 +38,7 @@
using namespace LAMMPS_NS;
#define MAX_GROUP 32
#define EPSILON 1.0e-6
enum{TYPE,MOLECULE,ID};
enum{LT,LE,GT,GE,EQ,NEQ,BETWEEN};
@ -1662,42 +1664,47 @@ void Group::inertia(int igroup, double *cm, double itensor[3][3], int iregion)
}
/* ----------------------------------------------------------------------
compute angular velocity omega from L = Iw, inverting I to solve for w
compute angular velocity omega from L and I
really not a group/region operation, but L,I were computed for a group/region
diagonalize I instead of inverting it, to allow for a singular matrix
------------------------------------------------------------------------- */
void Group::omega(double *angmom, double inertia[3][3], double *w)
{
double inverse[3][3];
double idiag[3],ex[3],ey[3],ez[3],cross[3];
double evectors[3][3];
int ierror = MathExtra::jacobi(inertia,idiag,evectors);
if (ierror) error->all(FLERR,
"Insufficient Jacobi rotations for group::omega");
inverse[0][0] = inertia[1][1]*inertia[2][2] - inertia[1][2]*inertia[2][1];
inverse[0][1] = -(inertia[0][1]*inertia[2][2] - inertia[0][2]*inertia[2][1]);
inverse[0][2] = inertia[0][1]*inertia[1][2] - inertia[0][2]*inertia[1][1];
inverse[1][0] = -(inertia[1][0]*inertia[2][2] - inertia[1][2]*inertia[2][0]);
inverse[1][1] = inertia[0][0]*inertia[2][2] - inertia[0][2]*inertia[2][0];
inverse[1][2] = -(inertia[0][0]*inertia[1][2] - inertia[0][2]*inertia[1][0]);
inverse[2][0] = inertia[1][0]*inertia[2][1] - inertia[1][1]*inertia[2][0];
inverse[2][1] = -(inertia[0][0]*inertia[2][1] - inertia[0][1]*inertia[2][0]);
inverse[2][2] = inertia[0][0]*inertia[1][1] - inertia[0][1]*inertia[1][0];
double determinant = inertia[0][0]*inertia[1][1]*inertia[2][2] +
inertia[0][1]*inertia[1][2]*inertia[2][0] +
inertia[0][2]*inertia[1][0]*inertia[2][1] -
inertia[0][0]*inertia[1][2]*inertia[2][1] -
inertia[0][1]*inertia[1][0]*inertia[2][2] -
inertia[2][0]*inertia[1][1]*inertia[0][2];
if (determinant > 0.0)
for (int i = 0; i < 3; i++)
for (int j = 0; j < 3; j++)
inverse[i][j] /= determinant;
w[0] = inverse[0][0]*angmom[0] + inverse[0][1]*angmom[1] +
inverse[0][2]*angmom[2];
w[1] = inverse[1][0]*angmom[0] + inverse[1][1]*angmom[1] +
inverse[1][2]*angmom[2];
w[2] = inverse[2][0]*angmom[0] + inverse[2][1]*angmom[1] +
inverse[2][2]*angmom[2];
ex[0] = evectors[0][0];
ex[1] = evectors[1][0];
ex[2] = evectors[2][0];
ey[0] = evectors[0][1];
ey[1] = evectors[1][1];
ey[2] = evectors[2][1];
ez[0] = evectors[0][2];
ez[1] = evectors[1][2];
ez[2] = evectors[2][2];
// enforce 3 evectors as a right-handed coordinate system
// flip 3rd vector if needed
MathExtra::cross3(ex,ey,cross);
if (MathExtra::dot3(cross,ez) < 0.0) MathExtra::negate3(ez);
// if any principal moment < scaled EPSILON, set to 0.0
double max;
max = MAX(idiag[0],idiag[1]);
max = MAX(max,idiag[2]);
if (idiag[0] < EPSILON*max) idiag[0] = 0.0;
if (idiag[1] < EPSILON*max) idiag[1] = 0.0;
if (idiag[2] < EPSILON*max) idiag[2] = 0.0;
// calculate omega using diagonalized inertia matrix
MathExtra::angmom_to_omega(angmom,ex,ey,ez,idiag,w);
}