Ma Zhaoyang

Monash University (Australia) · Department of Civil Engineering, Clayton

I am currently studying the nanoindentation of solids; currently I can obtain the Young's modulus and hardness of the solid material. However, I wanna observer the deformation process (especially the plastic deformation processing) during the simulation process. How can I achieve this aim?

Dear all,

I have alpha-quartz powders and I did 3 hours XRD scan for these powders both at 30 degrees Celsius and 450 degrees Celsius (there exists no phase transformation at this temperature). After refining by TOPAS-5, I wonder why my Rwp is 14% for 30 degrees and 19% for 450 degrees. Would you please check to see if the steps mentioned below are correct and Is the attached Rietveld refinement for silica done by TOPAS publishable? 

I want to use TOPAS to find out the effects of temperatures on unit cell parameters (trying to calculate the thermal expansion coefficient). I calculated the thermal expansion coefficient of alpha-quartz powders according to the change of the variation in unit cell parameters, as shown in the following table and this result is in accordance with other researcher's value.

Steps:

1- I loaded the scan file (30 degrees).  2- load the emission file. 

3- set the background order to 4 

4- loaded instrument details 

5- chose the correction (zero error, sample displacement, LP factor) 

6- start X from 22.5 because there exists a large disagreement between the actual scan pattern and fitted scan pattern before 22.5 degree

6- load the quartz.str file (PDF Card - 00-046-1045)

7- I changed all the occ and beg from fix to refine.

8- Run and check the Rwp value

9-Save structure in str format for 450 degrees (named as fitted-30degree.str)

Then for 450 degrees:

1- I loaded the scan file (450 degrees).  2- load the emission file.  3- set the background order to 4  4- loaded instrument details  5- chose the correction (zero error, sample displacement, LP factor)  6- start X from 22.5  6- load the fitted-30degree.str file  7- I changed all the occ and beg from fix to refine. 8- Run and check the Rwp value

Regards, Zhaoyang

I want to get the thermal expansion coefficient of each mineral in a rock using high-tempearture X-ray diffraction (XRD); how can we achieve that using TOPAS software, since there will be peak overlapping during the scan analysis.

What does “lennard-jones fluids” mean? It is a particular fluid type (e.g., water) or a collection of conceptual model for the fluids that satisfies the L-J potential?

I am a novice to LAMMPS and currently, I am reading a thesis named "2008  A molecular dynamics study of void initiation and growth in monocrystalline and nanocrystalline copper". In its appendix, the authors gave out the input script for the simulation, as shown follows:

units        metal boundary     p p p atom_style   atomic lattice      fcc 3.6150 origin 0 0 0 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1 region       box block -14 14 -14 14 -14 14 region       void sphere 0 0 0 10 units box create_box   1 box  create_atoms 1 region box group        bulk region box group        void region void delete_atoms group void pair_style   eam/alloy pair_coeff   * * cuMishinAlloy Cu neighbor     2.0 bin neigh_modify  every 1 delay 5 check yes compute       new3d all temp velocity      all create 300 14285736 temp new3d thermo        1  thermo_style  custom step temp pe ke etotal press vol lx ly lz pxx pyy pzz pxy pxz pyz thermo_modify temp new3d norm yes timestep      0.001 fix           1 all nve dump          1 all custom 5 dump.relax1.* x y z centro vx vy vz sxx syy szz sxy sxz syz tag epair ke restart       10 restart.relax1.* run           10

However, when I tried to run the script, it reminds me 

"ERROR on proc 0: Cannot open EAM potential file cuMishinAlloy (../pair_eam_alloy.cpp:131)

Last command: pair_coeff    * * cuMishinAlloy Cu"'

Hence, my question is where can I found the potential cuMishinAlloy? Thanks in advance.

Regards

In rock engineering, what's the definition of void and what's the relationship between void and fracture? For example, if I adopt molecular dynamics simulation to simulate the void in rocks (mineral), does this have any implication? Does the void evolution represents the variation of permeability value? Also, as shown in the thesis <a molecular dynamics study of void initiaton and growth in monocrystalline and nanocrystalline copper>, it refers to "fracture of ductile metals occurs by nucleation, growth and coalescence of void", what about rocks? Does the "fracture of "rock (mineral)" occurs by nucleation, growth and coalescence of void"?

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How can I draw the basic crystal of SiO4 and AlO6 using VESTA, can anybody give a hint?