/*
* Attempt to place an atom.
*/
bool Generator::attemptPlaceAtom(Atom& atom,
const DArray<double>& diameters,
CellList& cellList)
{
// Shift atom position to primary image within boundary
boundary().shift(atom.position());
Vector& pos = atom.position();
// Loop over neighbors, check distance to each.
// Return false immediately if any neighbor is too close.
CellList::NeighborArray neighbors;
cellList.getNeighbors(pos, neighbors);
double di = diameters[atom.typeId()];
double rSq, dj, dSq;
Atom* neighborPtr;
int n = neighbors.size();
for (int j = 0; j < n; ++j) {
neighborPtr = neighbors[j];
rSq = boundary().distanceSq(neighborPtr->position(), pos);
dj = diameters[neighborPtr->typeId()];
dSq = 0.5*(di + dj);
dSq *= dSq;
if (rSq < dSq) {
return false;
}
}
// If all neighbors are allowed, add atom to cellList
cellList.addAtom(atom);
return true;
}
/**
* Generate random molecules
*/
void Linear::generateMolecules(int nMolecule,
DArray<double> exclusionRadius, System& system,
BondPotential *bondPotentialPtr, const Boundary &boundary)
{
int iMol;
// Set up a cell list with twice the maxium exclusion radius as the
// cell size
double maxExclusionRadius = 0.0;
for (int iType = 0; iType < system.simulation().nAtomType(); iType++) {
if (exclusionRadius[iType] > maxExclusionRadius)
maxExclusionRadius = exclusionRadius[iType];
}
// the minimum cell size is twice the maxExclusionRadius,
// but to save memory, we take 2 times that value
CellList cellList;
cellList.allocate(system.simulation().atomCapacity(),
boundary, 2.0*2.0*maxExclusionRadius);
if (nMolecule > capacity())
UTIL_THROW("nMolecule > Species.capacity()!");
Simulation& sim = system.simulation();
for (iMol = 0; iMol < nMolecule; ++iMol) {
// Add a new molecule to the system
Molecule &newMolecule= sim.getMolecule(id());
system.addMolecule(newMolecule);
// Try placing atoms
bool moleculeHasBeenPlaced = false;
for (int iAttempt = 0; iAttempt< maxPlacementAttempts_; iAttempt++) {
// Place first atom
Vector pos;
system.boundary().randomPosition(system.simulation().random(),pos);
Atom &thisAtom = newMolecule.atom(0);
// check if the first atom can be placed at the new position
CellList::NeighborArray neighbors;
cellList.getNeighbors(pos, neighbors);
int nNeighbor = neighbors.size();
bool canBePlaced = true;
for (int j = 0; j < nNeighbor; ++j) {
Atom *jAtomPtr = neighbors[j];
double r = sqrt(system.boundary().distanceSq(
jAtomPtr->position(), pos));
if (r < (exclusionRadius[thisAtom.typeId()] +
exclusionRadius[jAtomPtr->typeId()])) {
canBePlaced = false;
break;
}
}
if (canBePlaced) {
thisAtom.position() = pos;
cellList.addAtom(thisAtom);
// Try to recursively place other atoms
if (tryPlaceAtom(newMolecule, 0, exclusionRadius, system,
cellList, bondPotentialPtr, system.boundary())) {
moleculeHasBeenPlaced = true;
break;
} else {
cellList.deleteAtom(thisAtom);
}
}
}
if (! moleculeHasBeenPlaced) {
std::ostringstream oss;
oss << "Failed to place molecule " << newMolecule.id();
UTIL_THROW(oss.str().c_str());
}
}
#if 0
// Check
for (int iMol =0; iMol < nMolecule; ++iMol) {
Molecule::AtomIterator atomIter;
system.molecule(id(),iMol).begin(atomIter);
for (; atomIter.notEnd(); ++atomIter) {
for (int jMol =0; jMol < nMolecule; ++jMol) {
Molecule::AtomIterator atomIter2;
system.molecule(id(),jMol).begin(atomIter2);
for (; atomIter2.notEnd(); ++atomIter2 ) {
if (atomIter2->id() != atomIter->id()) {
double r = sqrt(boundary.distanceSq(
atomIter->position(),atomIter2->position()));
if (r < (exclusionRadius[atomIter->typeId()]+
exclusionRadius[atomIter2->typeId()])) {
std::cout << r << std::endl;
UTIL_THROW("ERROR");
}
}
}
}
}
}
#endif
}
/**
* Recursive function to try to place an atom.
*/
bool Linear::tryPlaceAtom(Molecule& molecule, int atomId,
DArray<double> exclusionRadius, System& system, CellList &cellList,
BondPotential *bondPotentialPtr, const Boundary &boundary)
{
Atom& lastAtom = molecule.atom(atomId);
Atom& thisAtom = molecule.atom(++atomId);
Random& random = system.simulation().random();
bool hasBeenPlaced = false;
for (int iAttempt = 0; iAttempt < maxPlacementAttempts_; iAttempt++)
{
// draw a random bond vector
int beta = 1;
Vector v;
random.unitVector(v);
v *= bondPotentialPtr->randomBondLength(&random, beta,
calculateBondTypeId(lastAtom.indexInMolecule()));
Vector newPos;
newPos = lastAtom.position();
newPos += v;
// shift into simulation cell
boundary.shift(newPos);
// check if the atom can be placed at the new position
CellList::NeighborArray neighbors;
cellList.getNeighbors(newPos, neighbors);
int nNeighbor = neighbors.size();
bool canBePlaced = true;
for (int j = 0; j < nNeighbor; ++j) {
Atom *jAtomPtr = neighbors[j];
double r = sqrt(boundary.distanceSq(
jAtomPtr->position(), newPos));
if (r < (exclusionRadius[thisAtom.typeId()] +
exclusionRadius[jAtomPtr->typeId()])) {
canBePlaced = false;
break;
}
}
if (canBePlaced) {
// place the particle
thisAtom.position() = newPos;
// add to cell list
cellList.addAtom(thisAtom);
// are we add the end of the chain?
if (atomId == molecule.nAtom()-1)
return true;
// recursion step
if (! tryPlaceAtom(molecule, atomId, exclusionRadius, system,
cellList, bondPotentialPtr, boundary) ) {
// If the next monomer cannot be inserted, delete this monomer
// again
cellList.deleteAtom(thisAtom);
} else {
hasBeenPlaced = true;
break;
}
}
}
return hasBeenPlaced;
}
