Table 4.

Total energy drift of amino acid molecules in microcanonical ensemble simulation for 100 ps using SCC-DFTB at 298 K with different extrapolated DXL-BOMD algorithms and conventional approaches. Here, “PRC” denotes the algorithm use previous step converged charges as the initial guess of the current step geom. “ZRC” represents the algorithm that always starts from zero charge for each atom at every time step. The number under DXL-BOMD is higher odd order term remained in DXL-BOMD algorithms. The energy drift is taken as the different between the average energy of first 1000 steps and the final 1000 steps. The energy unit is 10⁻³ Kcal·mol⁻¹ ps⁻¹.

ASN			DXL-BOMD
SCF energy criteria[hartree]	PRC	ZRC	1	3	5	7	9	11	13
10−6	68.25	−0.37	5.77	0.07	−0.75	−1.31	2.43	3.51	1.46
10−7	6.73	0.25	0.28	−0.40	0.37	0.00	0.57	−0.10	−0.98
10−8	0.44	−0.14	0.19	0.06	0.17	−0.61	−0.28	−0.28	0.03
10−9	1.33	−0.07	−0.51	−0.16	−0.98	−0.39	−0.39	−0.25	0.43
10−10	−0.42	−0.32	−0.29	−0.63	−0.07	−0.15	−0.30	−0.08	0.13
GLU			DXL-BOMD
SCF energy criteria[hartree]	PRC	ZRC	1	3	5	7	9	11	13
10−6	303.10	0.30	14.77	−0.44	−0.35	0.92	6.09	11.10	−0.12
10−7	15.16	0.84	1.99	−0.20	−0.89	1.00	0.04	1.30	−0.73
10−8	1.94	0.37	−0.92	−0.09	0.62	0.40	2.00	−0.85	1.65
10−9	−0.21	−0.58	0.08	−0.22	0.92	−1.41	0.42	1.25	−1.51
10−10	1.33	1.08	0.17	0.83	0.85	1.05	0.10	−0.79	1.11
LYS			DXL−BOMD
SCF energy criteria[hartree]	PRC	ZRC	1	3	5	7	9	11	13
10−6	321.69	−2.05	38.11	−2.33	−0.43	−3.15	10.26	19.61	6.36
10−7	28.81	0.24	4.84	−0.86	1.77	−0.96	2.06	1.24	8.27
10−8	2.36	0.26	0.06	−0.70	0.42	2.75	0.76	1.44	0.52
10−9	0.93	−0.07	−1.08	0.71	1.54	−0.18	−0.15	−0.53	−0.62
10−10	1.19	0.60	0.12	−1.07	−0.41	1.07	−0.65	−0.01	0.45
TYR			DXL-BOMD
SCF energy criteria[hartree]	PRC	ZRC	1	3	5	7	9	11	13
10−6	207.20	0.42	13.27	1.27	0.49	0.08	3.99	14.21	32.82
10−7	15.22	0.57	1.97	−0.44	0.87	−0.47	0.61	2.74	8.01
10−8	1.51	−0.69	0.81	0.45	0.08	0.47	0.38	0.55	0.11
10−9	0.29	−0.44	1.14	1.08	0.85	0.05	0.35	0.37	0.95
10−10	−1.07	−0.15	0.51	1.30	0.68	0.39	1.20	0.40	0.01