### DEFINE SIMULATION BOX GEOMETRY ###
lattice sc 0.2
region box block 0 15 0 15 0 15
create_box 1 box
create_atoms 1 box

### DEFINE PHYSICAL PROPERTIES OF ATOMS ###
mass 1 1.0
pair_style lj/cut/opt 3.0
pair_coeff 1 1 1.0 1.0
neighbor 2.0 bin

### SPECIFY THE REQUIRED THERMODYNAMIC STATE ###
variable T equal 2.0
variable timestep equal 0.0025


### ASSIGN ATOMIC VELOCITIES ###
velocity all create ${T} 12345 dist gaussian rot yes mom yes

### SPECIFY ENSEMBLE ###
timestep ${timestep}
fix nve all nve

### THERMODYNAMIC OUTPUT CONTROL ###
thermo_style custom time etotal temp press 
thermo 10

### RECORD TRAJECTORY ###
dump traj all custom 1000 output-1 id x y z

### RUN SIMULATION TO MELT CRYSTAL ###
run 10000
unfix nve
reset_timestep 0

### BRING SYSTEM TO REQUIRED STATE ###
variable tdamp equal ${timestep}*100
fix nvt all nvt temp ${T} ${T} ${tdamp} 
run 10000
reset_timestep 0
unfix nvt
fix nve all nve 

### MEASURE SYSTEM STATE ###
thermo_style custom step etotal temp density atoms
variable dens equal density
variable temp equal temp
variable etotal equal etotal
variable etotal2 equal etotal*etotal 
variable atoms equal atoms 
fix aves all ave/time 100 1000 100000 v_dens v_temp v_etotal v_etotal2 v_atoms 
run 100000

variable avgdens equal f_aves[1]
variable avgtemp equal f_aves[2]
variable cv equal (f_aves[5]^2)*(f_aves[4]-f_aves[3]^2)/(f_aves[2]^2)

variable errdens equal sqrt(f_aves[4]-f_aves[1]*f_aves[1])
variable errtemp equal sqrt(f_aves[5]-f_aves[2]*f_aves[2])


print "Output"
print "--------"
print "Atoms: ${atoms}"
print "Density: ${avgdens}"
print "Stderr: ${errdens}"
print "Temperature: ${avgtemp}"
print "Stderr: ${errtemp}"
print "CV: ${cv}"