User:Jdz13

Equilibration TASK: Why do you think giving atoms random starting coordinates causes problems in simulations? Hint: what happens if two atoms happen to be generated close together? When two atoms are generated close together the potential energy generated with the atoms’ placement will be very large and the atoms will be pushed apart with a large velocity and potentially colliding with other atoms. This will create simulation system with a larger disorder with a very large initial energy. The problem is worsened due to periodic boundary conditions. In the system, the atoms are all enclosed inside a cubic box which is repeated infinitely in 3 dimensions. However when an atom reaches the boundary of the simulation box, a replica of it is produced at the other side of the simulation box so that the total number of atoms inside the box will remain constant. When this constantly happens due to many atoms traveling at a high velocity caused by close placement when generated, it will interfere with the conditions and dynamics set for the simulation, meaning that the data in the output files are not reporting on accurate data.

TASK: Satisfy yourself that this lattice spacing corresponds to a number density of lattice points of . Consider instead a face-centred cubic lattice with a lattice point number density of 1.2. What is the side length of the cubic unit cell? In one unit of a face-centred cubic lattice there are 8 atoms at each of the corners and 6 atoms on each of the faces. Each atom at the corner contribute 1/8 to the unit cell, while each atom on the face contribute ½ to the unit cell.

1/8×8+1/2×6=4 atoms in the unit cell Since the lattice point number density is 1.2. 4/1.2=3.33=Volume=〖Length〗^3 Length= ∛3.33=1.49 1.49 is the side length of the cubic unit cell.