Benchmark potential energy curve for collinear H3

A benchmark-quality potential energy curve is reported for the H$_3$ system in collinear nuclear configurations. The electronic Schr\"odinger equation solved using explicitly correlated Gaussian (ECG) basis functions an optimized fragment initialization technique that significantly reduces computational cost. As a result, computed energies improve upon recent orbital-based and ECG computations. Starting from well-converged set, with estimated sub-parts-per-billion precision generated series of configurations efficient rescaling approach.