bauer/lj_monte_carlo
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widom fixes

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This commit is contained in:
danijoo
2017-02-02 16:48:54 +01:00
parent af264ddef5
commit 8b9aa858ca
1 changed files with 41 additions and 32 deletions
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73
src/widom.rs
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@@ -12,18 +12,28 @@ const LJ_SIG : f64 = 1.0;
static MKSA_PLANCKS_CONSTANT_H : f64 = 1.0;
static MASS : f64 = 1.0;
const INSERTIONS_PER_STEP : usize = 1000;
const RUN_AVG_SIZE : usize = 100;
const RUN_AVG_SIZE : usize = 10;
const SHIFT : bool = true;
fn eval_ideal_potential(temperature: f64, lj_eps: f64, volume: f64, particles: f64, thermal_wavelength3: f64) -> f64 {
let density = volume/particles;
return -temperature/lj_eps * ( density*thermal_wavelength3 ).ln();
}
#[test]
fn test_eval_ideal_potential() {
let expected = 12.476649;
let result = eval_ideal_potential(2.0,1.0,10.0,512.0,0.1);
assert!((expected-result).abs() < 0.00001, "{}", result);
}
fn main() {
// parse args
let args: Vec<String> = env::args().collect();
let mut filename = "montecarlo.xyz".to_string();
let mut skip: usize = 0;
let mut insertions: usize = 100;
// liquid phase boundaries
let mut liquid_start = 0.0;
@@ -37,6 +47,8 @@ fn main() {
liquid_start = args[i + 1].parse::<f64>().unwrap();
} else if args[i] == "-le" {
liquid_end = args[i + 1].parse::<f64>().unwrap();
} else if args[i] == "-n" {
insertions = args[i+1].parse::<usize>().unwrap();
}
}
@@ -44,6 +56,7 @@ fn main() {
let mut trj_reader = TrjReader::new(&filename);
if skip > 0 { trj_reader.skip(skip) };
// trajectory information
let mut frame = trj_reader.next_frame();
println!("{:?}", frame);
@@ -55,25 +68,28 @@ fn main() {
// rnd number generator for particle insertion
let mut rng = rand::thread_rng();
// calculate liquid and gas volume
let liquid_height : f64 = liquid_end - liquid_start;
let liquid_volume = liquid_height * frame.box_x * frame.box_y;
let gas_volume = volume - liquid_volume;
// lambda = h/sqrt(2*pi*m*kb*T) = (2*pi*m*kb*T/h^2)^3/2
// this is lambda^3
let wave3 = ((2.0 * std::f64::consts::PI * MASS * frame.temperature / frame.lj_eps)/MKSA_PLANCKS_CONSTANT_H.powi(2)).powf(3.0/2.0);
// thermal wavelength to the power of 3 = h/sqrt(2*pi*m*kb*T) = (2*pi*m*kb*T/h^2)^3/2
let tw3 = ((2.0 * std::f64::consts::PI * MASS * frame.temperature / frame.lj_eps)/MKSA_PLANCKS_CONSTANT_H.powi(2)).powf(3.0/2.0);
// LJ shift
let e_shift = if SHIFT { 4.0 * LJ_EPS * ( (LJ_SIG/frame.lj_cutoff).powi(12) - (LJ_SIG/frame.lj_cutoff).powi(6) ) } else { 0.0 };
// average counters
let mut frame_count = 0;
let mut widom_sum_gas = 0.0;
let mut ideal_sum_gas = 0.0;
let mut ideal_pot_gas_sum = 0.0;
let mut widom_sum_liquid = 0.0;
let mut ideal_sum_liquid = 0.0;
let mut ideal_pot_liquid_sum = 0.0;
let mut avg_count = 0;
// loop over all frames
let mut counter = 0;
loop {
frame_count += 1;
@@ -85,9 +101,8 @@ fn main() {
else { gas_count += 1.0; }
}
// test particle insertion multiple times
for i in 0..INSERTIONS_PER_STEP {
// test particle insertion
for i in 0..insertions {
avg_count += 1;
// liquid test partcile
@@ -96,45 +111,39 @@ fn main() {
let lz = liquid_start + (liquid_height * rng.gen::<f64>());
let widom_e_liquid = get_particle_insertion_energy(&frame.rx, &frame.ry, &frame.rz, frame.num_particles, lx, ly, lz, frame.box_x, frame.box_y, frame.box_z, cutoff_sqr, e_shift);
widom_sum_liquid += (-beta*widom_e_liquid).exp();
// widom_sum_liquid += widom_e_liquid;
// gas test particle
let upper_or_lower = rng.gen::<bool>();
let gx = frame.box_x * rng.gen::<f64>();
let gy = frame.box_y * rng.gen::<f64>();
let gz;
if upper_or_lower {
gz = rng.gen::<f64>() * liquid_start;
} else {
gz = rng.gen::<f64>() * (frame.box_z - liquid_end) + liquid_end;
let mut gz = frame.box_z * rng.gen::<f64>();
while gz > liquid_start && gz < liquid_end { // retry until we have a particle in gas
gz= frame.box_z * rng.gen::<f64>();
}
let widom_e_gas = get_particle_insertion_energy(&frame.rx, &frame.ry, &frame.rz, frame.num_particles, gx, gy, gz, frame.box_x, frame.box_y, frame.box_z, cutoff_sqr, e_shift);
widom_sum_gas += (-beta*widom_e_gas).exp();
// widom_sum_gas += widom_e_gas;
// calculate ideal gas potential
ideal_sum_gas += -frame.temperature / frame.lj_eps * ((gas_volume/gas_count) * wave3).ln();
ideal_sum_liquid += frame.temperature / frame.lj_eps * ((liquid_volume/liquid_count) * wave3).ln();
// calculate ideal potentials
ideal_pot_gas_sum += eval_ideal_potential(frame.temperature, frame.lj_eps, gas_volume, gas_count, tw3);
ideal_pot_liquid_sum += eval_ideal_potential(frame.temperature, frame.lj_eps, liquid_volume, liquid_count, tw3);
}
// print running averages
if avg_count / INSERTIONS_PER_STEP > RUN_AVG_SIZE {
let ideal_gas = ideal_sum_gas / avg_count as f64;
let ideal_liquid = ideal_sum_liquid / avg_count as f64;
// let excess_gas = - (widom_sum_gas/avg_count as f64).ln()/beta;
// let excess_liquid = - (widom_sum_liquid/avg_count as f64).ln()/beta;
if avg_count / insertions > RUN_AVG_SIZE {
let ideal_gas_potential = ideal_pot_gas_sum / avg_count as f64;
let ideal_liquid_potential = ideal_pot_liquid_sum / avg_count as f64;
let excess_gas = -(widom_sum_gas/avg_count as f64).ln()/beta;
let excess_liquid = -(widom_sum_liquid/avg_count as f64).ln()/beta;
let gas_total = ideal_gas + excess_gas;
let liquid_total = ideal_liquid + excess_liquid;
println!("Frame {}\tg_ex: {:5}\tl_ex: {:5}\tg_tot: {:5}\tl_tot: {:5}\t\tnparticles: {}/{}", frame_count, excess_gas, excess_liquid, gas_total, liquid_total, gas_count, liquid_count);
let mut gas_total = ideal_gas_potential + excess_gas;
let liquid_total = ideal_liquid_potential + excess_liquid;
println!("Frame {}\tg_ex: {:5}\tl_ex: {:5}\tg_tot: {:5}\tl_tot: {:5}\t\tnparticles: {}/{}", frame_count, excess_gas, excess_liquid, if gas_total.is_infinite() { 0.0 } else { gas_total } , liquid_total, gas_count, liquid_count);
// println!("Frame {}\tgas {}\tliquid {}\t particles gas/liquid:{}/{}", frame_count, ideal_gas + excess_gas, ideal_liquid + excess_liquid, gas_count, liquid_count);
// reset averages for next round
avg_count = 0;
ideal_sum_gas = 0.0;
ideal_sum_liquid = 0.0;
ideal_pot_gas_sum = 0.0;
ideal_pot_liquid_sum = 0.0;
widom_sum_gas = 0.0;
widom_sum_liquid = 0.0;
}