# Tag Info

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I will start with acronyms for coupled-cluster, and someone else might answer with acronyms for basis sets or for functionals or for many body perturbation theory or for composite approaches or for different types of SCF: Coupled Cluster acronyms CCSD, CCSDT, CCSDTQ, ... (coupled cluster with singles, doubles, triples, quadrtuples, etc.) CCSD(T), CCSDT(Q), ...

20

I'm just as curious of a user here as you, but I was able to find that a Materials Modeling Wikipedia page does in fact exist. :) Computational materials science and engineering uses modeling, simulation, theory, and informatics to understand materials. Main goals include discovering new materials, determining material behavior and mechanisms, ...

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"Matter modeling" is a term that was coined by Stack Exchangers! That's why the words "matter" and "modeling" next to each other, don't seem to exist in any of the results in a Google search of "Matter Modeling", apart from this Stack Exchange site, Adam Iaizzi's blog post about this SE site, and maybe our community's ...

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You can see it with VESTA software. For example, we can see the different lattice planes of NaCl crystal. [001] plane of NaCl: [101] plane of NaCl: [111] plane of NaCl:

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CDFT: Current DFT Current DFT is defined via the generalized Hohenberg-Kohn theorem (HKT), which extends the traditional HKT to account for the effect of magnetic fields. The generalized HKT says that the scalar potential $\mathbf{V}$, the (nondegenerate) ground state wavefunction $\Psi$, and the vector potential $\mathbf{A}$ are uniquely determined by the ...

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"Mio" refers to "Million" and "CPUh" is the abbreviation of CPU hours, also refered to as Core hours. This is a good read if you need to know more about HPC. This is an interesting reddit post on the same topic.

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Answering your last questions: yes, yes and yes. One thing to consider is which approach do you want/need to use. You can use an atomistic approach where you simulate/model the properties and the material starting from the atomic structure of it (an input file with the list of atoms and its coordinates). The other approach is to use your material as a ...

15

OF-DFT: Orbital-free density functional theory Hohenberg and Kohn established that the ground state energy, $E$, of interacting electrons in a potential, $v(\mathbf{r})$, is a functional of the electron density, $n(\mathbf{r})$: $$\tag{1} E[n] = F[n] + \int \mathrm{d}\mathbf{r} \, v(\mathbf{r}) n(\mathbf{r}) .$$ While this statement is formally true, we do ...

15

What is a force field? The Wikipedia entry on this is a good resource, but I'll give my own description below. In the context of molecular dynamics (MD), a force field is one way of describing the interactions between atoms. In classical MD, the motion of atoms is determined by the instantaneous forces acting on the atoms (i.e., we need forces in order to ...

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First Principles mean starting directly at the level of established science and not making assumptions such as any empirical models or parameter fitting. With respect to DFT, EMF (Electromagnetic force) is a very strong force governing nucleus and electrons (referring to a single atom). With that, atoms, molecules, macro molecules and materials are built up....

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Assuming a generic chemistry background I wouldn't assume that knowledge of crystal structure would be too in depth at an undergraduate level. It is definitely encountered, but depending on the type of chemistry you want to go into, you probably never deal with solid state chemistry. I would first explain briefly how crystals are described by periodic ...

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CPMD: Car-Parrinello Molecular Dynamics An approximation of BOMD (Born-Oppenheimer MD) where fictitious dynamics is used on the electrons to keep them close to their ground state, so that we do not have to keep solving for their ground state at every single step. We start with Newton's 2nd law (as does classical MD), but instead of the force being calculated ...

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I don't think it's ideal, but there is the term "base metal". There are various definitions for what is considered a base metal, but the main noble (or precious) metals are always excluded. Some definitions also exclude ferrous metals. Unfortunately, this variation in meaning means it might be better to just say "non-ferrous, non-noble", ...

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The anions of the form $\ce{MnO_x^y-}$ are referred to as manganates (see Wikipedia). I'm not sure if there might be a "special" name for $\ce{MnO2^-}$ specifically (that's the species you have here) because I never encountered this anion in my lab times, but given that $\ce{MnO4^2-}$ are the "normal" manganates and $\ce{MnO4^-}$ the permanganates, I think ...

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Density Functionals LDA (LSDA): S: Slater (Dirac) exchange functional for a uniform electron gas. VWN: Vosko, Wilk, and Nusair 1980 correlation functional fitting the random phase approximation solution to the uniform electron gas. PL: Perdew and Wang 1992 local correlation functional (also known as PW or PW92). PZ81: Perdew-Zunger parameterization of the ...

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First of all, we assume the matter is constituted by nuclei and electrons, as illustrated by the following figure: Mathematically, the matter is mapped into the following Hamiltonian: $$H=T_e + T_n + V_{ee} + V_{nn} + V_{en} \tag{1}$$ which is called the standard model of condensed matter physics. In principle, all information (ground state/excited state/...

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Basis Sets Throughout, I use square brackets to denote additional options that can be included, but are not required. Slater: STO-nG: Slater Type Orbitals represented by a function of n contracted Gaussian functions Pople: X-YZG: Split valence double zeta basis functions, where each core orbital is represented by a contracted function on X primitive ...

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The $\Sigma$ values represent the volume of the Coincident Site Lattice (CSL) of the grain boundary in terms of the volume of the unit cell of the crystal. In general, grain boundaries with higher symmetry have lower $\Sigma$ values. Note that CSL boundaries are special grain boundaries. So, they do not represent all grain boundaries comprehensively. But, ...

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By making a supercell and modifying it in some way, you are creating an entirely new structure which you hope can give you some insight by being compared to the original structure. Any of the conclusions you draw from your calculations will come from the modified supercell, rather than a version where you have converted it back into the primitive cell. Some ...

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I am curious to know if the word has been used in any way other than the above three ways. Mark. J. Winter at University of Sheffield has used the word differently — not as a term meaning something specific, but as a name for the so-called Sheffield ChemPuter: Welcome to the University of Sheffield's ChemPuter, a set of simple interactive calculators for ...

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The term chemputer also refers to a universal chemical synthesis robot - this is because the robot uses a high level abstraction of chemical synthesis. From this approach we developed a programming language for chemistry that can be run on the chemputer robot. Since in principle ANY chemical can be made in our robot, and the langauge is universal, we coined ...

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Density functional perturbation theory (DFPT) This method refers to the calculation of the linear response of the system under some external perturbation. Consider some set of parameters $\{\lambda_i\}$. The first and second derivatives of the total energy with respect to these parameters in DFT read: $$\frac{\partial E}{\partial\lambda_i}=\int\frac{\... 7 2nd Generation CPMD Car-Parrinello MD avoids repeatedly solving the electronic problem by propagating the orbitals as if they were particles governed by Newton's equations. This is much more efficient than having to solve at each time step as is done in Born-Oppenheimer MD, though at the cost of decreasing the maximum timestep for the dynamics (too large a ... 7 The term's origin goes back to vector field which is a function that returns a vector for any given point in space (as in the image below on the left). We can almost "see" that such fields exist, by putting iron filings and a magnet on a sheet of paper (the magnetic field causes the iron filings to move accordingly): In classical molecular ... 6 HPCs work by allowing you to run jobs on many computers with many CPUs in parallel. CPUh refers to how many CPUs are being used for how long (the h in CPUh stands for hours). For instance, you may have a job that needs 64 CPUs and will run for a whole day. That would be 1536 CPU hours. The largest jobs I see on our (relatively small) HPC are 128 CPUs for ... 6 When your lattice is primitive you have only the (0,0,0)+ set; when your lattice has some kind of centering (body- or face-centering) other sets are present, such as (1/2, 1/2, 1/2)+ or (1/2, 1/2, 0)+ It's not clear to me what you write. In the first page of the Internationl Tables you find all the symmetry operations that are listed with Roman numerals (1),(... 6 ab initio Ehrenfest Dynamics From Li et.al.,2005, JCP "The Born Oppenheimer (BO) and extended Lagrangian (EL) trajectories are founded on the assumption that a single electronic potential surface governs the dynamics. .. A major limitation of adiabatic trajectories is that they are not applicable to reactions involving nonadiabatic electronic processes, ... 6 Quantum Monte Carlo What are the types of Quantum Monte Carlo? Methods SSE QMC: Stochastic Series Expansion QMC SAC: Stochastic Analytic Continuation (an add-on technique for real-time dynamics) VMC: Variational Monte Carlo DMC: Diffusion Monte Carlo t-VMC: Time-dependent variational Monte Carlo CT-QMC: Continuous time QMC DDQMC (or DDMC): [Diagrammatic ... 6 KS-DFT: Kohn-Sham DFT The KS-DFT is proposed to deal with the problems of orbital-free DFT (OFDFT), which has been explained by @wcw. OFDFT attempts to compute the energy of interacting electrons, as the functional of the density. While this brute force approach is in principle correct, in practice it is not very accurate. This is due to the lack of accurate ... 6 Real-time TDDFT (RT-TDDFT) This is the straightforward non-perturbative solution of the TDDFT equations by means of direct propagation in time. Pioneered by Theilhaber and Yabana & Bertsch it has since found its way into several molecular or solid-state codes. The TDDFT equations in the Kohn–Sham (KS) framework are$$ i \frac{\partial}{\partial t} \phi_i ...

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