deficiencies.html
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deficiencies.html
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			LAMMPS Deficiencies</H2>
			<P>
			<A HREF="README.html">Return</A> to top-level of LAMMPS documentation.</P>
			<P>
			This is a brief list of features lacking in the current version of
			LAMMPS. Some of these deficiencies are because of lack of
			time/interest; others are just hard!</P>
			<UL>
			<LI>
			The calculation of pressure does not include a long-range Van der Waals
			correction. This would be a constant for constant volume simulations
			but is a source of error for constant pressure simulations where
			the box-size varies dynamically.
			<LI>
			The smoothed Coulomb style cannot be used with class 2 force fields.
			<LI>
			The minimizer does not work with constant pressure conditions, nor
			for some kinds of fixes (constraints).
			<LI>
			No support for non-rectilinear boxes (e.g. Parinello-Rahman
			pressure control).
			<LI>
			SHAKE fixes cannot be combined with rREPSA.
			<LI>
			In the current F90 version of LAMMPS, Ewald computations are 2x slower
			on some machines than they were in the earlier F77 version. This is
			probably because of F90 compiler treatment of allocatable arrays. This
			slowdown is not an issue with PPPM, which is more commonly used anyway.
			<LI>
			LAMMPS uses a spatial-decomposition of the simulation domain, but no
			other load-balancing -- thus some geometries or density fluctuations can
			lead to load imbalance on a parallel machine.
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