Dear all

I am calculating viscosity for CuZr metallic glass at different temperature starting from 700- 1400, when i plot log**eta** vs **1000/T,** i expect it to some what like super-Arrhenius ,but as from the output it doesn’t seems to happen, also this viscosity is of order 10^-3 pa.s (**for normal alloy**) althought it should be order of 10^12 (**for glassy alloy**) pa.s, as My RDF shows that my alloy system has turned out to be glass, so can any one tell **where am i making mistake?**

**Viscosity seems to be more for less atoms and less for more atoms** peculiar ???

**2.** Also when i keep correlation length 2.75 Angstrom, then on single processor it runs ok but when i run it for 4 processor it gives: **Expected integer parameter in input script or data file …(keeping correlation length 2 or 2.75 A has no change on viscosity order i.e 10^-3)**

**1.viscosity variation for large number of atoms** (**around 40000 atoms**)is

700 **0.00203786**423029241

750 **0.00200799**988986868

800 **0.00211236**02482052

850 0.00221549426324076

900 0.00206741594788209

950 0.00238465374610291

1000 0.00203833138326794

1050 0.00196192035370546

1100 0.00210520959677994

1150 0.0025774401726619

1200 0.00217181118480748

1250 0.00255080602755192

1300 **0.003549793**52196017

1350 0.00271862986371651

1400 **0.003031080**39351355

1450 0.00263496537084788

**2.For small no of atoms** (**around 900 atoms**)

1300 **0.022491467**3906881

1250 **0.02069912**82553045

1200 0.0270304491212631

1150 0.0411253048231375

1100 0.0989126318827202

1050 0.0402150564851684

1000 0.0412556077162107

950 0.0276721530959114

900 0.0490452908599106

850 0.0272939715677626

800 0.0387311847639487

750 **0.0259791**517843982

My program for viscosity calculation is

**Sample LAMMPS input script for viscosity of Glassy CuZr alloy**

variable T equal 750

variable V equal vol

variable dt equal 0.002

variable p equal 2 # correlation length (**from auto-correlation function it is 2 Angstrom**)

variable s equal 50 # sample interval

variable d equal $p*$s # dump interval

# convert from LAMMPS real units to SI

variable kB equal 1.3806504e-23 # [J/K/ Boltzmann

variable atm2Pa equal 101325.0

variable A2m equal 1.0e-10

variable ps2s equal 1.0e-12

variable convert equal {atm2Pa}*{atm2Pa}*{ps2s}*{A2m}*{A2m}*{A2m}

# setup problem

units metal

echo both

atom_style atomic

dimension 3

boundary p p p

region box block 0 20 0 20 0 20 units box

create_box 2 box

lattice fcc 3.61 orient x 2 0 0 orient y 0 2 0 orient z 0 0 2

region cu block 0 20 0 20 0 20 units box

create_atoms 1 region cu units box

set region cu type/fraction 2 0.5 12393

pair_style eam/fs

pair_coeff * * …/…/…/…/…/potentials/CuZr_mm.eam.fs Cu Zr

minimize 1.0e-4 1.0e-6 100000 100000

run_style verlet

timestep ${dt}

thermo $d

thermo_style custom step temp pe etotal press vol

# equilibration and thermalization

velocity all create $T 102486 mom yes rot yes dist gaussian

fix NVT all nvt temp $T $T 10 drag 0.2

run 20000

# viscosity calculation, switch to NVE if desired

#unfix NVT

#fix NPT all npt

reset_timestep 0

variable pxy equal pxy

variable pxz equal pxz

variable pyz equal pyz

fix SS all ave/correlate $s $p $d &

v_pxy v_pxz v_pyz type auto file Cu5Zr5.dat ave running

variable scale equal {convert}/({kB}*$T)*$V*s*{dt}

variable v11 equal trap(f_SS[3])*{scale}
variable v22 equal trap(f_SS[4])*{scale}
variable v33 equal trap(f_SS[5])*${scale}

thermo_style custom step temp press v_pxy v_pxz v_pyz v_v11 v_v22 v_v33

run 100000

variable v equal (v_v11+v_v22+v_v33)/3.0

variable ndens equal count(all)/vol

print “average viscosity: $v [Pa.s/ @ T K, {ndens} /A^3”

Thanks in advance

Regards

Anik