Thank you sir, for your reply but I have one particular molecular system of 10-20 atoms which I am getting from a simulation of a large atom (around 10000 atoms) at a 300K temperature from a molecular dynamic simulation (LAMMPS). and I also did optimization of that MD structure which is amorphous metallic glass. Now, Can I do dft study of a small part of a single molecule of a large MD simulation(~10000 atoms) ? till now i did below things but i am bit confused which way is best way to study DFT . i also dis AIMD/CPMD but for metallic glass CPMD doesn't work good with PAW PP. so, 1. Can I do direct SCF calculation(without relax) by giving a condition of *forc_conv_thr* and *tot_conv_thr* with creating a vacuum(for a non-periodic system) of around 15 Angstrom to converge properly. *OR* 2. I should do the RELAX calculation with vacuum and then go to the *scf* calculation to find the total energy and then *nscf*.
***questions: 1. what if I relax a system and position is changed a bit(which is obvious) to minimize the total energy but that energy is at zero kelvin dft calculation and I want to study the system at 300K. So how can small parts of a structure reflect large MD simulation structural properties? Thank you regards jayraj anadani Ph.D. Research scholar Department of physics sardar patel university india On Fri, Aug 26, 2022 at 5:00 PM Stefano de Gironcoli <[email protected]> wrote: > Dear JAYRAJ ANADANI, > > calculation="scf" corresponds to a minimization of the total energy > at fixed atomic positions. you chose where to put the ions. the code > does its best to return the corresponding energy. > > calculaiton="relax" corresponds to a series of scf calculations, > followed by forces evaluation and geometry update to minimize the energy > of the system. The code does its best to converge to a minimum (non > necessarily the global minimum) in the GS potential energy surface. > > there is no temperature in any of these calculations. > > if you want to simulate the system at finite (classical) temperature > for the atoms you should perform MD simlations > > stefano > > On 26/08/22 05:02, Jayraj Anadani wrote: > > Dear QE > > I put H2O molecular atoms small far apart from each > > other within large supercell so that the periodic image of the H2O do > > not interact with each other and run a scf calculation my convergence > > done successfully with good amount of accuracy upto 10^-9. But it is > > not reflecting original H2O molecule at 300 Kelvin...but when i > > relaxing these atoms and then did scf calculation they are reflecting > > H2O at 300k by observing bond angel and length.. how ? And my question is > > 1) scf is also doing calculation using iteration method algorithm by > > using electronic densities at ground state so why they converge when > > two hydrogen atoms and one oxygen atom are not at appropriate > > distance.still scf converge how ? > > 2) also by doing relax calculation all of sudden two hydrogen and one > > oxygen come closer and they formed a bond and bond angel which is > > reflect 300k H2O molecule structure. So how two hydrogen and one > > oxygen atoms knows during relaxation that i have to make structure at > > a room temperature? > > > > > > Thank you > > Regards > > > > JAYRAJ ANADANI > > Ph.D Research scholar > > Department of physics > > Sardar Patel University > > Anand,Gujarat, > > India > > > > _______________________________________________ > > The Quantum ESPRESSO community stands by the Ukrainian > > people and expresses its concerns about the devastating > > effects that the Russian military offensive has on their > > country and on the free and peaceful scientific, cultural, > > and economic cooperation amongst peoples > > _______________________________________________ > > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > > users mailing list [email protected] > > https://lists.quantum-espresso.org/mailman/listinfo/users > _______________________________________________ > The Quantum ESPRESSO community stands by the Ukrainian > people and expresses its concerns about the devastating > effects that the Russian military offensive has on their > country and on the free and peaceful scientific, cultural, > and economic cooperation amongst peoples > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ The Quantum ESPRESSO community stands by the Ukrainian people and expresses its concerns about the devastating effects that the Russian military offensive has on their country and on the free and peaceful scientific, cultural, and economic cooperation amongst peoples _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
