First-Principles Calculations of the Structure Stability and Mechanical Properties of LiFeAs and NaFeAs under Pressure

Table 1

Calculated lattice constants (a and c in Å) and primitive cell volume (V in ų) for tetragonal LiFeAs and NaFeAs under different pressures (P in GPa) at 0 K.

P	LiFeAs			NaFeAs
	a	c	V	a	c	V
0	3.791	6.112	87.840	3.929	6.890	106.361
5	3.718	5.949	82.236	3.858	6.610	98.384
10	3.660	5.835	78.163	3.795	6.466	93.123
15	3.614	5.741	74.983	3.742	6.361	89.070
16	3.605	5.723	74.376	3.732	6.344	88.358
17	3.597	5.707	73.839	3.723	6.327	87.697
18	—	—	—	3.714	6.311	87.053
19	—	—	—	3.705	6.295	86.412