Respected Sir, Sorry for so many queries. In the paper of S Q Wang et al. J Phys. Cond. Matter 15 (2003) 5307, He uses three types of strains
1. Tri-axial shear strain to calculate C44 2. volume conservative orthorombic strain to calculate shear modulus C` and 3. Hydrostatic pressure to calculate Bulk modulus. In my calculations, on applying the 3rd strain, I am getting different volumes (Volume non-conserve) and 1st & 2nd type volume remain conserve. Because in order to calculate 3 elastic constants (C11, C12 and C44) we require 3 equations, so do I have to use the above three equations, both type (volume conservative and non-conservative) to calculate a single set of elastic constants? Bipul Rakshit PhD in Physics Computational Research Lab. Barkatullah University, Bhopal 462 026, India Mob.: +919713445650 --- On Wed, 15/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: From: Sushil Auluck <saul...@iitk.ac.in> Subject: Re: [*] Re: [SIESTA-L] question about elastic constant To: "bipul rakshit" <bipu...@yahoo.co.in> Date: Wednesday, 15 July, 2009, 8:56 PM bipul, you can have 2 kinds of strains...volume conserving and volume non conserving...each gives different elastic constants..... s.auluck > Dear Sir, > I have one more doubt, that, if I calculate the set of lattice vector, > applying the following strains >   e = (δ, δ, (1 + δ)^ (−2) − 1, 0, 0, 0) > > as given in the paper attached with this mail, > > then the cell volume was not remain constant for all the lattice vectors. > Means for different lattice vectors, the cell volume changes. > > But for other two set of strains > e = (0, 0, 0, δ, δ, δ) > and e =(δ, δ, δ, 0, 0, 0) > the cell volume doesnt change for all the lattice vector. > > So is it the correct method I am applying? Or there should be no change of > cell volume? > >  delta E/V = 6*C*δ^2 + O(δ^3 > ).                        (7) > V > > > Bipul Rakshit > > PhD in Physics > > Computational Research Lab. > > Barkatullah University, > > Bhopal 462 026, India > > Mob.: +919713445650 > > --- On Wed, 15/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: > > From: Sushil Auluck <saul...@iitk.ac.in> > Subject: Re: [*] Re: [SIESTA-L] question about elastic constant > To: bipu...@yahoo.co.in > Date: Wednesday, 15 July, 2009, 7:01 PM > > bipul, > if you look at the derivation you will find terms like (1+d)**(1/2) > or (1+d)**(1/3)....d is delta.....so when you expand using binomial > theorem you will terms linear in d, quadratic in d, and cubic in d... > in this context the series is terminated after the quadratic and so > the remaining terms ( these are niglected) are order d**3..... > s.auluck > >> Respected Sushil Auluck, >> Thanks for your kind reply. As you said that the term means of order >> delta >> cube. >> But I just want to know the equation of that term. Means how that order >> delta cube, mathematically looks like. I asked this because, using that >> equation, I have to find the elastic constants. >> regards >> >> Bipul Rakshit >> >> PhD in Physics >> >> Computational Research Lab. >> >> Barkatullah University, >> >> Bhopal 462 026, India >> >> Mob.: +919713445650 >> >> --- On Mon, 13/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: >> >> From: Sushil Auluck <saul...@iitk.ac.in> >> Subject: Re: [SIESTA-L] question about elastic constant >> To: SIESTA-L@listserv.uam.es >> Date: Monday, 13 July, 2009, 9:48 PM >> >> hi, >> that means terms of order delta cubed (delta**3)...... >> s.auluck >> >>> Dear Siesta Users, >>> I have read the paper >>> "S. Q. Wang, H. Q. Ye, J. Phys.: Condens. Matter 15 (2003) p. 5307." >>>  >>> Most of the thing is clear to me, except in Equation (7) what is >>> "O(δ^3)" >>> ? What does 'O' here. >>> >>> >>> Please guide me for the same. >>> >>> >>> Bipul Rakshit >>> >>> PhD in Physics >>> >>> Computational Research Lab. >>> >>> Barkatullah University, >>> >>> Bhopal 462 026, India >>> >>> Mob.: +919713445650 >>> >>> >>>     See the Web's breaking stories, chosen by people like you.. >>> Check >>> out Yahoo! Buzz. http://in.buzz.yahoo.com/ >> >> >> ........................................................................ >> Prof. Sushil Auluck           >> Phone:+91-512-6797092/6148 >> Department of Physics             >> +91-512-6798177(Home) >> Indian Institute of Technology       Cell :+91-9305548667 >> Kanpur 208016 (UP)             Fax >> :+91-512-6790914 >> India                  >> E-mail:saul...@iitk.ac.in    >>  >>    ................................................:saul...@gmail.com >> http://www.iitk.ac.in/phy/People/phy_facvis.html >> http://www.iitk.ac.in/phy/New01/profile_SA.html >> ........................................................................ >> ~ >> >> >> >>     See the Web's breaking stories, chosen by people like you. >> Check >> out Yahoo! Buzz. http://in.buzz.yahoo.com/ > > > ........................................................................ > Prof. Sushil Auluck           > Phone:+91-512-6797092/6148 > Department of Physics             > +91-512-6798177(Home) > Indian Institute of Technology       Cell :+91-9305548667 > Kanpur 208016 (UP)             Fax > :+91-512-6790914 > India                  > E-mail:saul...@iitk..ac.in    >     ................................................:saul...@gmail.com > http://www.iitk.ac.in/phy/People/phy_facvis.html > http://www.iitk.ac.in/phy/New01/profile_SA.html > ........................................................................ > ~ > > > > See the Web's breaking stories, chosen by people like you. Check > out Yahoo! Buzz. http://in.buzz.yahoo.com/ ........................................................................ Prof. Sushil Auluck Phone:+91-512-6797092/6148 Department of Physics +91-512-6798177(Home) Indian Institute of Technology Cell :+91-9305548667 Kanpur 208016 (UP) Fax :+91-512-6790914 India E-mail:saul...@iitk..ac.in ...............................................:saul...@gmail.com http://www.iitk.ac.in/phy/People/phy_facvis.html http://www.iitk.ac.in/phy/New01/profile_SA.html ........................................................................ ~ Love Cricket? Check out live scores, photos, video highlights and more. Click here http://cricket.yahoo.com
