# Tag Info

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You may want to have a look at this paper: "Geometry optimization made simple with translation and rotation coordinates" https://aip.scitation.org/doi/10.1063/1.4952956 This is not a comprehensive benchmark but it does contain a few examples ranging from water clusters of 12 water molecules to small proteins. According to this paper Cartesian ...

11

We performed some timing benchmarks as part of our recent paper, albeit not on molecular dynamics: "Assessing conformer energies using electronic structure and machine learning methods" Int J Quantum Chem. 2020; 121:e26381 It was a bit controversial, since we compared single-core CPU times and not in batch mode. Once the ML method runs the model, ...

9

There are many options to answer your question. Just to compare the computation time, the first condition is to run the simulations with the same hardware i.e. in the same system (two different set-ups even with the same type of hardware can perform differently). Also, both codes have to be compiled with the same compiler and with the same compiling ...

8

General vs segmented contraction Unless one is using a fully decontracted a.k.a "primitive" basis set, one uses contracted Gaussian-type orbitals (cGTOs), which are given as a linear combination of the primitive Gaussian-type orbitals (pGTOs): $\chi_i^\text{cGTO}({\bf r}) = \sum_{\alpha} d_{\alpha i} \chi_\alpha^\text{pGTO}({\bf r})$. ...

8

Integral Screening It is possible to place upper bounds on integrals based on the Cauchy-Schwartz inequality: $$\left( a a | b b \right) \ge \left( a c | b d \right)$$ If the first integral is computed and deemed insignificant, the latter is as well. One can further combine this with the appropriate density matrix element and decide that the resulting ...

6

What's the best way to compare two DFT codes? I assume here the DFT means Kohn-Sham density functional theory (KS-DFT). The central task of KS-DFT is to solve the following Kohn-Sham equation (atomic unit is adopted): $$\left[-\dfrac{1}{2}\nabla^2+V_{ks}[\psi_i(\vec{r})]\right]\psi_i(\vec{r})=E_i\psi_i(\vec{r})$$ which is a nonlinear differential equation ...

6

MOLPRO Continuing Susi's excellent benchmarking for $\ce{Zn}$ and $\ce{Zn_2}$, MOLPRO 2012 gives for $\ce{Zn}$: RHF-SCF energy: -1777.84665521 CPU time for INT: 0.42 SEC CPU time for RHF: 0.01 SEC Disk used for INT: 12.87 MB However the RHF energy was converged already at iteration 1, so there wasn't much work to do: ITERATION DDIFF ...

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