|From:||Axel Kohlmeyer <akohlmey@...24...>|
|Date:||Thu, 17 Aug 2017 16:49:11 -0400|
Thanks for quick reply,Artificial setup means dont we suppose to use that?
For the first , i want to melt it at 0 bar pressure. so i am tracking pressure.
yes i try to visualise the system but as i start from restart file in next step it suddenly contract in z even temperature is increasing.Before starting of simulation it has length in z about 40 angstroms and in next step it become 38.4.even i am not observing appropriate expansion during heating what we expect from bulk melting.
On 18 August 2017 at 00:05, Axel Kohlmeyer <akohlmey@...24...> wrote:On Thu, Aug 17, 2017 at 1:13 PM, Prakash Makwana <pmakwana9005@...24...> wrote:hello all,i am doing simulation for aluminium.I intitially heated crystal uoto 800K. now what i need to do is to create two group.Then heat one group to temperature higher thanthe melting temperature and keep the other group atoms fixed.i need to heat such that its x and y dimension remain unchanged. so i applled barostate in z direction only.But as i know that barostate is applied to whole system.so how can i correct the barostate.?this is a rather artificial setup, why bother with a barostat at all? unless there is a significant expansion upon melting, you could just keep the volume or otherwise compute the expected change in volume for the melting part and use the change_box command to expand the box as needed, and then run with fixed volume.To apply thermostat to group i used fix_modify and to fix atoms of other group, i exclude it from time integration. i thought that i should turn off solid group interaction\so i used neigh_modify command .can anyone please tell me neigh_modify can correct barostat or not?I am writing script here.i observed that the temperature of group which is heated suddenly increse from 800K to 1200K and then decrese slowely during inital timesteps.But if i run same script made for alumina then there is no any increase in themperature is observed.sO Is there any difference between this? please look the below scriptand tell me what did i do wrong.what temperature reported how?have you visualized your system? did you see anything out of the ordinary?please note, that you have to be extremely careful when moving only part of the atoms with the box change. you can quickly create large overlaps. you have to watch where you place the origin of the cell. again, my main suggestion is to side-step all the headaches and worries and just run with a fixed volume.axel.------------------------------i named the heating group as liquid and fix group as solid.region box block -0.15 20.5 -0.135 20.5 19.0 40.9 units boxread_restart stage1.restart.130000region box1 block -0.15 20.5 -0.135 20.5 -0.2 19.0 units boxregion box2 block -0.15 20.5 -0.135 20.5 19.0 40.9 units boxgroup solid region box1group liquid region box2#potentialpair_style eam/alloypair_coeff * * Al.in Alcompute 1 all pevariable pressure equal pressvariable peatom equal (pe/atoms)variable mass_g equal mass(all)/6.02e23variable vol_cm3 equal vol*1.0e-24variable density equal v_mass_g/v_vol_cm3variable teatom equal (etotal/atoms)compute le liquid pe/atomcompute lo liquid reduce sum c_levariable leatom equal (c_lo)/(960)compute se solid pe/atomcompute so solid reduce sum c_sevariable seatom equal (c_so)/(960)compute t_s solid tempcompute t_l liquid tempcompute te all temp#compute p_l liquid pressure NULL#pressure in solidcompute s1 solid stress/atom NULLcompute ps solid reduce/region box1 sum c_s1 c_s1 c_s1variable solidpress equal -(c_ps+c_ps+c_ps)/(3*
20*17*26)variable sxx equal -(c_ps)/(20*17*26)variable syy equal -(c_ps)/(20*17*26)variable szz equal -(c_ps)/(20*17*26)#pressure in liquidcompute l1 liquid stress/atom NULLcompute pl liquid reduce/region box2 sum c_l1 c_l1 c_l1variable liquidpress equal -(c_pl+c_pl+c_pl)/(3* 20*17*26)variable lxx equal -(c_pl)/(20*17*26)variable lyy equal -(c_pl)/(20*17*26)variable lzz equal -(c_pl)/(20*17*26)thermo_style custom step c_t_s c_t_l temp press v_sxx v_syy v_szz v_lxx v_lyy v_lzz pxx pyy pzz v_leatom v_seatom lzneigh_modify exclude group solid solidrestart 150000 stage2.restartlog log.heat1500fix 3 liquid npt temp 800 1500 1.0 z 0.0 0.0 1.0 dilate liquidfix_modify 3 temp t_lrun 70000unfix 3 ------------------------------ ------------------
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